OC-005 ENDOSCOPIC SURGICAL SKILL QUALIFICATION SYSTEM IN JAPAN: PROVEN PERFORMANCE IN HERNIA SURGERY

Endoscopic Surgical Skill Qualification System by Japan Society for Endoscopic Surgery is implemented from 2004.

Laparoscopic inguinal hernia repair (TAPP, TEP) is positioned as a low difficulty level operation under general surgery field in this system.

An application qualification to the system demands the list of a specified operative cases, to participate in education seminars, and training of endoscopic surgery over 2 years after the Board Certified.

A specified case quantity is the operative experience of above 5 examples of a high-difficulty level and 45 examples of a low difficulty level operation.

Candidates submit 3 no edited videos of the endoscopic surgery performed for indirect hernia with the orifice above 1.5 cm in a male-sex. Which to examine among 3 videos is decided randomly by the society.

Two hernia-specified referees examine one candidate. When both results don't agree, an extra referee will examine newly and fixes the result.

An evaluation is estimated within 60 points of common standards and 40 points by an hernia. Equal to or more than 70 points in amount become a pass. Acceptance rate in hernia was 16% in 2021.

The Nationwide Survey of Endoscopic Surgery reported recurrence rates of after laparoscopic hernia surgery as 5% in TEP in and 4% in TAPP in 2012–2013, 2.0% and 1.3% in 2018∼2019, what is improved beyond the period.

It's no exaggeration to say that the Qualification System has played a big part.

The Qualification System like no other in the world is to be introduced.

High tumor mutation burden fails to predict immune checkpoint blockade response across all cancer types

BACKGROUND

High tumor mutation burden (TMB-H) has been proposed as a predictive biomarker for response to immune checkpoint blockade (ICB), largely due to the potential for tumor mutations to generate immunogenic neoantigens. Despite recent pan-cancer approval of ICB treatment for any TMB-H tumor, as assessed by the targeted FoundationOne CDx assay in nine tumor types, the utility of this biomarker has not been fully demonstrated across all cancers.

PATIENTS AND METHODS

Data from over 10 000 patient tumors included in The Cancer Genome Atlas were used to compare approaches to determine TMB and identify the correlation between predicted neoantigen load and CD8 T cells. Association of TMB with ICB treatment outcomes was analyzed by both objective response rates (ORRs, N = 1551) and overall survival (OS, N = 1936).

RESULTS

In cancer types where CD8 T-cell levels positively correlated with neoantigen load, such as melanoma, lung, and bladder cancers, TMB-H tumors exhibited a 39.8% ORR to ICB [95% confidence interval (CI) 34.9-44.8], which was significantly higher than that observed in low TMB (TMB-L) tumors [odds ratio (OR) = 4.1, 95% CI 2.9-5.8, P < 2 × 10^-16]. In cancer types that showed no relationship between CD8 T-cell levels and neoantigen load, such as breast cancer, prostate cancer, and glioma, TMB-H tumors failed to achieve a 20% ORR (ORR = 15.3%, 95% CI 9.2-23.4, P = 0.95), and exhibited a significantly lower ORR relative to TMB-L tumors (OR = 0.46, 95% CI 0.24-0.88, P = 0.02). Bulk ORRs were not significantly different between the two categories of tumors (P = 0.10) for patient cohorts assessed. Equivalent results were obtained by analyzing OS and by treating TMB as a continuous variable.

CONCLUSIONS

Our analysis failed to support application of TMB-H as a biomarker for treatment with ICB in all solid cancer types. Further tumor type-specific studies are warranted.

Combined pathologic-genomic algorithm for early-stage breast cancer improves cost-effective use of the 21-gene recurrence score assay

Background

The 21-gene recurrence score (RS) (Oncotype DX®; Genomic Health, Redwood City, CA) partitions hormone receptor positive, node negative breast cancers into three risk groups for recurrence. The Anne Arundel Medical Center (AAMC) model has previously been shown to accurately predict RS risk categories using standard pathology data. A pathologic-genomic (P-G) algorithm then is presented using the AAMC model and reserving the RS assay only for AAMC intermediate-risk patients.

Patients and methods

A survival analysis was done using a prospectively collected institutional database of newly diagnosed invasive breast cancers that underwent RS assay testing from February 2005 to May 2015. Patients were assigned to risk categories based on the AAMC model. Using Kaplan-Meier methods, 5-year distant recurrence rates (DRR) were evaluated within each risk group and compared between AAMC and RS-defined risk groups. Five-year DRR were calculated for the P-G algorithm and compared with DRR for RS risk groups and the AAMC model's risk groups.

Results

A total of 1268 cases were included. Five-year DRR were similar between the AAMC low-risk group (2.7%, n = 322) and the RS < 18 low-risk group (3.4%, n = 703), as well as between the AAMC high-risk group (22.8%, n = 230) and the RS > 30 high-risk group (23.0%, n = 141). Using the P-G algorithm, more patients were categorized as either low or high risk and the distant metastasis rate was 3.3% for the low-risk group (n = 739) and 24.2% for the high-risk group (n = 272). Using the P-G algorithm, 44% (552/1268) of patients would have avoided RS testing.

Conclusions

AAMC model is capable of predicting 5-year recurrences in high- and low-risk groups similar to RS. Further, using the P-G algorithm, reserving RS for AAMC intermediate cases, results in larger low- and high-risk groups with similar prognostic accuracy. Thus, the P-G algorithm reliably identifies a significant portion of patients unlikely to benefit from RS assay and with improved ability to categorize risk.

Abstract OT1-03-04: INTERACT- INTegrated Evaluation of Resistance and Actionability using Circulating Tumor DNA in hormone receptor (HR) positive metastatic breast cancers (MBC)

Background

Mutations in the ligand-binding domain of ESR1 have been demonstrated to mediate resistance to aromatase inhibitors (AI) and are associated with poor survival. Analyses of circulating tumor DNA (ctDNA) offer a minimally invasive and real-time approach to characterize genomic landscape, clonal evolution, and treatment response. Early detection and intervention with alternate therapy to overcome resistance at minimal disease burden progression could have a larger impact than treating higher burden disease at clinical progression. However, whether treatment decisions made based on the emergence of secondary resistance mutations or mutant allele fraction (MAF) changes in ctDNA can improve clinical outcomes is unknown. Currently, the most effective therapy for patients harboring ESR1 mutations is unclear; although, pre-clinical and retrospective clinical trial analyses have suggested that some of these mutations may exhibit greater sensitivity to fulvestrant, a selective estrogen receptor down-regulator, compared to AI. This study hypothesizes that real-time monitoring of ctDNA for secondary ESR1 alterations can identify subclinical progression and early intervention with a targeted-agent that has greater efficacy against ESR1 mutations can improve disease-free survival.

Trial Design

This is a randomized, open-label, Phase-2 study for HR-positive MBC patients who are on AI and CDK 4/6 inhibitor as first line therapy. Patients on treatment for at least 12 months without evidence of clinical progression would be screened for ESR1 mutations using Guardant360 ctDNA assay. Patients with positive ESR1 mutations would be randomized to change of endocrine therapy to fulvestrant vs. continuing AI.

Eligibility criteria

-Histologically confirmed HR-positive (ER and/or PR &gt;10%) and HER2-negative MBC

-On AI with CDK4/6 inhibitor as first line therapy for 12 months without evidence of clinical progression

-Activating ESR1 mutation identified on ctDNA

-ECOG performance status ≤1

-Normal organ and marrow function

Specific aims

- To assess progression-free survival (PFS) with transition to fulvestrant compared with continuing AI therapy in patients with emergence of ESR1 mutations in plasma

-To assess ctDNA ESR1 mutant allele fraction and kinetics with transition to fulvestrant compared with AI

-To assess the prevalence of ESR1 mutations in patients with exposure to endocrine therapy

-To assess overall survival with fulvestrant transition compared with continuing AI therapy in patients with emergence of ESR1 mutations

Statistical methods

To detect a change in median PFS from 5 months (for AI arm) to 9 months (with fulvestrant arm) would require about 124 patients (5% two-sided alpha, 80% power, log rank testing). Interim analysis will be performed when 42 PFS events are observed. Using O'Brien-Fleming stopping boundaries, we will stop for futility if the log rank test p-value &gt; 0.72 and stop for success if it is &lt; 0.004.

Citation Format: Damodaran S, Meric-Bernstam F, Hess KR, Litton JK, Raymond V, Lanman R, Ueno NT, Hamilton S, Wistuba II, Valero V, Moulder SL, Tripathy D. INTERACT- INTegrated Evaluation of Resistance and Actionability using Circulating Tumor DNA in hormone receptor (HR) positive metastatic breast cancers (MBC) [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr OT1-03-04.

Abstract P5-17-06: Immune modulation with humanized anti-EGFR antibody panitumumab in an immunocompetent mouse model for inflammatory breast cancer

Background: Inflammatory breast cancer (IBC) is the most lethal and aggressive form of breast cancer and there are no approved targeted therapies specifically for IBC. Targeting the epidermal growth factor receptor (EGFR) pathway is a promising therapeutic target for patients with triple-negative IBC (TN-IBC) with a reported pathological complete response rate of 42% (JAMA Oncology, 2018). The tumor microenvironment (TME) is a critical contributor to the aggressiveness of IBC. Delineating cross-talk between EGFR-targeted therapies and TME components, which define IBC, could inform more efficient combination regimens and novel clinical trial designs for IBC. However, such studies have not been conducted due to the lack of a syngeneic IBC mouse model. Here we report the establishment of an IBC immunocompetent mouse model and the effects of panitumumab (PmAb) on IBC tumor growth and the TME.

Methods: TN-IBC cell lines, SUM149 or FC-IBC-02, were mixed with 50% Matrigel and inoculated into mammary fat pads of hu-NSG-SGM3 mice engrafted with hematopoietic stem cells (The Jackson Laboratory). SUM149 tumor growth in hu-NSG-SGM3 mice treated with either IgG2 (isotype control, 4 mg/kg) or PmAb (1 mg/kg and 4 mg/kg) was measured. The percentages of TME components, including human CD4+ T, CD8+ T, regulatory T (Tregs), and natural killer (NK) cells, and M1 or M2 macrophages, in the peripheral blood and tumor tissues treated with IgG2 and PmAb for 7 weeks were measured by flow cytometry.

Results: Hu-NSG-SGM3 mice supported the growth of TN-IBC SUM149 and FC-IBC-02 xenografts. These humanized mouse models were named SUM149-huSGM3 and FC-IBC-02-huSGM3, respectively. Analysis of the blood cells showed that SUM149-huSGM3 mice display human CD4+ T, CD8+ T, Tregs, M1 and M2 macrophages. T cell infiltration and M1 and M2 macrophages were also detected in SUM149-huSGM3 tumors. NK cells were not detected in both peripheral blood and tumors. PmAb treated SUM149-huSGM3 mice had significantly reduced SUM149 tumor growth, compared with mice that received the IgG2 control. PmAb treatment increased the percentage of CD8+ T cells and reduced the percentage of Tregs in peripheral blood. A similar analysis of tumor infiltrating lymphocytes isolated from each group showed an increase in percent CD8+ T cells in mice treated with PmAb. There were no significant changes of M1 or M2 macrophages following PmAb treatment. These results suggest that the increase in percentage of CD8+ T cells in peripheral blood and IBC tumors, and the decrease in percentage of Tregs in peripheral blood may contribute to the therapeutic efficacy of PmAb.

Conclusion: We established the first immunocompetent mouse model to study the TME and immune response in IBC, which provides the premise for conducting a diversity of novel preclinical therapeutic studies. The mechanism of how immune responses of TN-IBC xenografts mediates the therapeutic efficacy of PmAb in IBC tumors needs to be further investigated. Our study also suggests that combination therapy with immune checkpoint inhibitors may potentiate the efficacy of anti-EGFR therapy in IBC. The therapeutic efficacy of PmAb and anti-PD-L1 combination in SUM149 humanized mice is in progress.

Citation Format: Wang X, Shao S, Pearson T, Cheng Y, Reuben JM, Tripathy D, Ueno NT. Immune modulation with humanized anti-EGFR antibody panitumumab in an immunocompetent mouse model for inflammatory breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-17-06.

Abstract P2-01-03: Lipocalin 2 promotes inflammatory breast cancer tumorigenesis and skin invasion

Background: Inflammatory breast cancer (IBC) is the most lethal form of primary breast cancer and accounts for a significant 10 % of breast cancer deaths in the USA owing to its aggressive proliferation and metastasis, and a lack of effective therapeutic options. Unraveling the underlying mechanisms of growth and metastasis of this aggressive disease could lead to effective therapeutic strategies for an improved outcome in IBC patients. We recently generated in vitro and in vivo IBC models for brain metastasis studies [Debeb et al. JNCI, 2016] and observed an upregulation of Lipocalin 2 (LCN2), a small, secreted iron-trafficking protein which plays a significant role in immune and inflammatory responses and the promotion of malignant progression. The purpose of this study was to investigate the function of LCN2 in IBC tumorigenesis and metastasis.

Methods: Stable knockdown (KD) of LCN2 in IBC cell lines was achieved with lentiviral vectors. Proteomic and gene expression profiling were performed using RPPA and Affymetrix Clariom D microarray. For in vivo studies, control and LCN2 KD IBC cells were transplanted into the cleared mammary fat pad of SCID/Beige mice. Tumor-skin involvement was assessed visually during primary tumor growth and tumor excision. LCN2 gene expression levels in clinical samples were analyzed from the IBC Consortium as well as public data sets. LCN2 serum levels in IBC patients were measured using ELISA and were correlated with clinicopathological variables and outcome data.

Results: LCN2 gene expression is higher in IBC versus non-IBC patients (p=0.00036), independently of the molecular subtypes, and higher in more aggressive (TNBC and HER2+) than hormone receptor-positive subtypes (p&lt;0.00001). LCN2 expression in patient tissues is correlated with reduced overall survival (p&lt;0.00001) and metastasis-free survival (p=0.04) in non-IBC; however, LCN2 was not associated with overall survival in IBC patient serum samples. LCN2 expression was also significantly higher in IBC cell lines, in their culture media, and in brain metastasis sublines compared to non-IBC cell lines (p=0.004). In IBC cell lines, LCN2 KD reduced proliferation, colony formation, migration, and cancer stem cell properties. In vivo silencing of LCN2 in SUM149 cells inhibited primary tumor growth (p=0.001)and resulted in a well-differentiated tumor histology. Additionally, SUM149 LCN2 KD significantly reduced skin invasion/recurrence (LCN2 control vs LCN2 KD: 88 % vs 25 %, p=0.01) suggesting LCN2 is a mediator of tumorigenesis. Analysis of proteomics data showed changes in major signaling pathways including PI3K-Akt signaling and EGF/EGFR signaling pathways. Mechanistically, LCN2 depletion in SUM149 abrogated EGF-induced EGFR phosphorylation and ERK activation.

Conclusions: Our findings suggest that LCN2 may drive IBC tumor progression and skin invasion/recurrence potentially via the EGFR signaling pathway.Future studies will determine the role of LCN2 in metastasis and pinpoint the detailed mechanisms of LCN2-mediated IBC tumorigenesis and recurrence.

Citation Format: Villodre ES, Larson R, Hu X, Stecklein SR, Gomez K, Finetti P, Krishnamurthy S, Ivan C, Su X, Ueno NT, Van Laere S, Bertucci F, Tripathy D, Vivas-Mejía P, A Woodward W, Debeb BG. Lipocalin 2 promotes inflammatory breast cancer tumorigenesis and skin invasion [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-01-03.

Abstract P3-08-02: Withdrawn

This abstract was withdrawn by the authors.

Citation Format: Harano K, Wang Y, Masuda H, Lim B, Parinyanitikul N, Lee H-J, Seitz RS, Morris SW, Bailey DB, Hout DR, Rao A, Lucci A, Tripathy D, Krishnamurthy S, Ueno NT. Withdrawn [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-08-02.

Abstract P3-10-23: Changes in the expression of HER2 and other genes in HER2-positive metastatic breast cancer induced by treatment with ado-trastuzumab emtansine and/or pertuzumab/trastuzumab

Background: Although tremendous progress has been achieved with targeted therapy for HER2-positive (HER2+) metastatic breast cancer, most advanced tumors eventually develop resistance. Improving our understanding of mechanisms of resistance to anti-HER2 therapy is needed to develop new therapeutic approaches. The purpose of this study was to identify the mechanisms of resistance to treatment with ado-trastuzumab emtansine (T-DM1) and/or taxane/pertuzumab/trastuzumab (TPH).

Methods: In our preclinical analysis, HER2+ cell lines resistant to treatment with T-DM1 (n=5), and pertuzumab/trastuzumab (n=3) were generated. HER2 expression in the original and resistant cell lines was compared using Western blot, and HER2 gene amplification was compared in them using fluorescence in situ hybridization (FISH) and a Droplet Digital Polymerase Chain Reaction HER2 copy-number-validation assay. In our clinical analysis, nine patients with HER2+ metastatic breast cancer who had progressed on T-DM1 and/or TPH were enrolled. Patients underwent biopsies following treatment with T-DM1 and/or TPH. Targeted next-generation sequencing was performed using the FoundationOne® assay (Foundation Medicine, Inc.) to identify gene alterations. Also, the HER2 expression before and after the therapy was compared using immunohistochemistry and/or FISH.

Results: In preclinical analysis, HER2 expression/amplification by Western blot and gene copy-number analysis was significantly decreased in T-DM1–resistant cell lines (four of five cell lines; P &lt; 0.01) but not in pertuzumab/trastuzumab-resistant cell lines (none of three cell lines). In clinical analysis, the patients' median age was 54 years (range, 45-77 years), and five patients (56%) were ER+. Five patients (56%) received first-line anti-HER2 therapy, and four patients (44%) received two lines of anti-HER2 therapy prior to enrollment. We observed loss of HER2 expression in four of nine patients (44%) after undergoing anti-HER2 therapy. After receiving TPH, one of eight patients (13%) lost HER2 positivity according to FISH. In contrast, after T-DM1, three of four tested patients (75%) lost HER2 amplification by FISH. As for next-generation sequencing, we analyzed seven samples: three after treatment with TPH and four after treatment with T-DM1. In four of these samples (57%), we observed loss of HER2 amplification: one after treatment with TPH and three after treatment with T-DM1. TP53 mutations were seen in all patients. Additionally, we observed TOP2A and MCL1 amplification in two patients with ERBB2 amplificationand AKT1 amplification in one patient with ERBB2 amplification loss.

Conclusions: We show for the first time that T-DM1–resistant breast cancer cells lose HER2 expression and amplification. Additionally, we observed loss of HER2 expression in patient samples following treatment with HER2 targeted therapy. Further study of resistant tumor samples is required to understand the impact of HER2 loss on outcomes. For the time being, repeating biopsy analysis of a metastatic site after treatment with T-DM1 to determine the HER2 expression status is reasonable, and it may increase the efficacy of future anti-HER2 therapy.

Citation Format: Kida K, Lee J, Liu H, Lim B, Murthy RK, Sahin AA, Tripathy D, Ueno NT. Changes in the expression of HER2 and other genes in HER2-positive metastatic breast cancer induced by treatment with ado-trastuzumab emtansine and/or pertuzumab/trastuzumab [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-10-23.

Abstract P2-06-05: TP-0903, an AXL kinase inhibitor, reduces inflammatory breast cancer aggressiveness and macrophage polarization through additional mechanisms that may include JAK2 and Aurora B

Background: Inflammatory breast cancer (IBC) is the most lethal and aggressive type of breast cancer; it accounts for 2-4% of breast cancer cases but causes 8-10% of breast cancer deaths. Novel targeted therapy to improve the outcomes of patients with IBC is urgently needed. The receptor tyrosine kinase AXL is a driver for metastasis and drug resistance in various cancers, including breast cancer. Our previous work showed that AXL signaling contributes to the aggressiveness of IBC. In addition, emerging evidence indicates that the tumor microenvironment components, particularly tumor-associated macrophages, are critical drivers of the IBC clinical phenotype and promote IBC metastasis. AXL signaling has been shown to modulate the tumor microenvironment. In the present study, we investigated the impact of TP-0903, a small-molecule AXL kinase inhibitor, with additional activity against Aurora B and Janus kinase 2 (JAK2), on IBC cells and macrophage polarization.

Methods: The effects of TP-0903 on IBC cell proliferation, migration/invasion, and mammosphere formation were analyzed. The effects of TP-0903 on the polarization of human monocytic cells THP-1 were tested in vitro. In addition, the signaling pathways involved in TP-0903-regulated M2 macrophage polarization were investigated using Western blotting.

Results: The half-maximal inhibitory concentration (IC50) of TP-0903 in an array of IBC cells (including SUM149, SUM190, BCX010, FC-IBC-02, MDA-IBC-3, and KPL4) ranged from 66 nM to 346 nM, suggesting a strong cell growth inhibitory effect. TP-0903 treatment decreased the migration, invasion, and mammosphere formation of IBC cells. In addition, TP-0903 inhibited both AXL signaling and Aurora B activation, which induced a G2/M cell cycle arrest in IBC cells. Based on the importance of AXL and JAK2 in the regulation of the tumor microenvironment, we showed that TP-0903 decreased expression of CD163/CD206 and the CCL17/CCL18 cytokine, and markers of M2 macrophages, suggesting that TP-0903 treatment inhibits the polarization of THP-1 cells to M2 macrophages in vitro. We also found that TP-0903 treatment decreased the phosphorylation of STAT6, a critical molecule in M2 polarization, and that knockdown of STAT6 expression decreased M2 macrophage polarization, indicating that TP-0903 may regulate macrophage polarization via STAT6 signaling.

Conclusion: Our results demonstrated the dual functions of TP-0903 targeting of both IBC cells and macrophages, possibly via the targeting of multiple kinases, including AXL and Aurora B. Examinations of the impact of TP-0903 on the cross-talk between IBC cells and macrophages in vitro and in vivo and the related mechanisms are ongoing and will be presented at the meeting.

Citation Format: Cheng Y, Funakoshi Y, Wang X, Warner SL, Bearss DJ, Ueno NT. TP-0903, an AXL kinase inhibitor, reduces inflammatory breast cancer aggressiveness and macrophage polarization through additional mechanisms that may include JAK2 and Aurora B [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-06-05.

Abstract P6-17-04: 3-year relapse-free survival of stage II-III HER2-neu positive breast cancer treated with pertuzumab and trastuzumab-containing neoadjuvant therapy compared to trastuzumab-containing therapy

Background: Pertuzumab (P) in combination with trastuzumab (H) based chemotherapy is FDA-approved as a standard neoadjuvant treatment for patients with clinical stage II-III HER2-positive (HER2+) breast cancer (BC). The goal of this study was to evaluate the pathologic complete response (pCR) rate for neoadjuvant HP-containing regimens compared to H-containing regimens and report the 3-year relapse-free survival (RFS) for patients who had a pCR compared to those with residual disease (RD).

Methods: All patients with stage II-III non-inflammatory HER2+ BC who received neoadjuvant H-containing or HP-containing therapy and underwent definitive breast and axillary surgery were identified from 2005 to 2016 through an institutional database. Medical records were examined for patient demographics, breast cancer stage, pathology results, surgical outcomes, and treatment details. pCR was defined as ypT0/is, ypN0. RFS was defined as the interval from surgery to date of last followup or death from any cause. Descriptive statistics, Cox proportional hazards, and Kaplan-Meier estimates were used for statistical analysis.

Results: Patient characteristics and results by pCR or RD status are shown in the table below. The median age was 51 (22-84) years for the HP group and 50 (21-87) years for the H group. The median follow-up time was 1.9 (0-4.2) years for the HP group and 5.3 (0.1-12) years for the H group. For the HP group, the 3-year RFS was 98% (95% CI: 95, 100) for the pCR group and 90% (95% CI: 83, 97) for the RD group; HR 0.17 (0.04, 0.82), p=0.012. For the H group, the 3-year RFS was 91% (95% CI: 88,94) for the pCR group and 75% (95% CI: 71-79) for the RD group; HR 0.31 (0.22, 0.44), p&lt;0.0001. Among the 520 patients who achieved pCR and the 502 patients who had RD, the effect of HP vs. H was statistically significant (pCR: HR 0.24 (0.06, 1.00); p=0.015) (no pCR: HR 0.46 (0.22, 0.94); p=0.017).

Conclusion: Patients who achieve pCR have an improved 3-year RFS compared to patients who have RD. Treatment with HP-containing neoadjuvant regimens is associated with a high 3-year RFS.

VariableHP (n=215)H (n=807)  pCR n=121RD n=94pCR n=399RD n= 408Age at Diagnosis&lt;5043%46%46%51% ≥5057%54%54%49%Menopausal StatusPremenopausal46%50%53%57% Postmenopausal54%50%47%43%Clinical Stage at DiagnosisIIA40%29%34%29% IIB29%31%23%28% IIIA14%15%17%16% IIIB0%5%5%9% IIIC17%20%21%18%Clinical Nodal StatusNode (+)63%76%69%73% Node (-)37%24%31%27%Nuclear Grade1II25%32%22%28% III75%65%78%72%HR statusHR(+)52%74%52%67% HR(-)48%26%48%33%Adjuvant therapyTrastuzumab88%80%100%100% Trastuzumab and Pertuzumab3%5%0%0% Unknown9%15%20%0%11 patient in the HP pCR group had nuclear grade 1; 2 patients in the HP RD group had nuclear grade 1 tumors 2 2 patients received adjuvant TDM-1 on the NSABP B50 protocol

Citation Format: Murthy RK, Raghavendra AS, Hess KR, Barcenas CH, Lim B, Moulder SL, Giordano SH, Mittendorf EA, Thompson A, Ueno NT, Valero V, Litton JK, Tripathy D, Chavez-Macgregor M. 3-year relapse-free survival of stage II-III HER2-neu positive breast cancer treated with pertuzumab and trastuzumab-containing neoadjuvant therapy compared to trastuzumab-containing therapy [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-17-04.

Abstract P4-02-05: Apocrine morphology and LAR molecular subtype predict prognosis of TNBC patients with residual disease after neoadjuvant chemotherapy

Background: TNBC molecular subtype classification updated by Lehmann et al. includes 4 subtypes: basal-like 1 and 2 (BL1), (BL2), mesenchymal (M), and luminal androgen receptor (LAR), and as a modifier of these subtypes, an Immunomodulatory (IM) gene expression signature. However, molecular subtypes have not been linked to morphological features of TNBC. Apocrine carcinoma has been proposed as a TNBC category that expresses androgen receptor. LAR-subtype TNBC has a poor response to neoadjuvant systemic therapy (NST). We hypothesized that defining the apocrine-featured TNBC by morphology and molecular subtype predict the prognosis of patients with residual disease after NST. Methods: We created the Pan-Pacific TNBC Consortium dataset, which contains paired samples of matched pre and post-NST TNBC tumors from 4 institutions. All patients received NST and didn't have a pathological complete response (pCR). Three pathologists examined hematoxylin and eosin-stained slides of 86 pre-NST samples and determined (1) the presence of apocrine differentiation, (2) the level of tumor-infiltrating lymphocytes (TILs), (3) the histological grade (HG), and (4) the rate of necrosis. These morphological features were compared among the subtypes. For a sample to be considered apocrine positive, apocrine differentiation had to be identified by 2 or more pathologists. Fisher's exact test was used to test the association of subtypes and morphological features. The log-rank test was used to compare disease-free survival (DFS). Results: Twelve of 24 (50%) apocrine-positive tumor samples were LAR subtype, and12 of 17 (70%) LAR-subtype tumor samples exhibited apocrine differentiation. The other subtypes showed following: BL1, 11/44 (25%); BL2, 0/7 (0%); M, 1/10 (10%); unclassified, 0/8 (0%). The median follow-up time was 22 months. In all populations, 2-year DFS rates were higher in patients with apocrine-positive tumors than in those whose tumors did not exhibit apocrine differentiation (P = .027; 2-year DFS, 85% vs 54%). The LAR subtype was also associated with lower HG, although LAR tumors had a similar prognosis to the other subtypes. In the combined analysis of subtypes and apocrine differentiation, patients with apocrine-positive LAR tumors had a higher 2-year DFS rate than did those with apocrine-negative LAR tumors (P = .044; 2-year DFS, 88% vs. 30%). However, patients with apocrine-positive BL1 tumors had no better DFS than did those with apocrine-negative BL1 tumors (P = .133). TIL levels and the presence of the IM signature were positively associated (P = .01), and apocrine differentiation positivity tended to be negatively associated with TIL level (P = .06). Neither TIL level nor IM signature was associated with survival. Conclusion: Apocrine differentiation was associated with the LAR subtype of TNBC and better prognosis in patients who did not have a pCR. The LAR subtype alone did not predict DFS; however, LAR tumors with apocrine differentiation had a better prognosis than did LAR tumors without apocrine differentiation. Using a combination of morphologic and genomic testing may be helpful in determining the prognosis of patients with apocrine-positive TNBC tumors who have residual disease after NST.

Citation Format: Masuda H, Miura S, Harano K, Wang Y, Hirota Y, Matsunaga Y, Lim B, Lucci A, Parinyanitikul N, Lee HJ, Gong G, Rao A, Seitz RS, Morris SW, Hout DR, Nakamura S, Tripathy D, Harada O, Krishnamurthy S, Ueno NT. Apocrine morphology and LAR molecular subtype predict prognosis of TNBC patients with residual disease after neoadjuvant chemotherapy [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P4-02-05.

Abstract P5-05-10: Estrogen receptor β suppresses metastasis of inflammatory breast cancer by regulating cell cytoskeleton and cytokine signaling

Inflammatory breast cancer (IBC) is the most lethal form of breast cancer that accounts for about 10% of breast cancer mortality annually in US. Poor prognosis is largely due to the high propensity of IBC tumors to develop distant metastasis that occurs directly from the gland epithelium and through lymphatic invasion in which dermal lymphatics are filled with tumor emboli. Owing to the complex metastatic process, the molecular basis of IBC aggressiveness is poorly understood, and no specific therapeutic target has been identified. Despite the lack of estrogen receptor α (ERα) in the majority of IBC tumors, estrogen may still play a role in these cancers through pathways that involve ERβ. Our tissue staining reveals expression of ERβ in more than 50% of IBCs that is reproduced in IBC cell lines. Furthermore, analysis of IBC datasets indicates correlation of receptor expression with good prognosis. We studied this association in preclinical models of IBC by knocking out ERβ in IBC cells. This promotes migration and invasion through cytoskeleton remodeling whereas re-expression of the receptor in knockout cells restores the cytoskeletal structure and migration to the levels of control cells. Consistent with increased migration, deletion of ERβ activates large gene networks of cell de-differentiation and cytokine synthesis that trigger tumor microenvironment responses to promote the motile phenotype of IBC cells. In contrast, ligands that activate the receptor inhibit signaling that contributes to metastasis in IBC. Analysis of an orthotopic xenograft model shows that IBC tumors lacking ERβ have higher propensity for metastasis compared with the ERβ-proficient tumors supporting the anti-metastatic activity of the receptor. Our findings point towards a role of ERβ in preventing distant metastases by inhibiting dissemination of IBC cells and maintaining the integrity of emboli. This function combined with distinct expression indicates the potential of ERβ to represent a unique prognostic marker and therapeutic target that can be utilized to repress IBC metastasis and eliminate its associated mortality.

Citation Format: Thomas C, Karagounis I, Srivastava RK, Kumar S, Karar J, Chao H-H, Kazimierczak A, Bado I, Nikolos F, Leli N, Koumenis C, Krishnamurthy S, Ueno NT, Chakrabarti R, Maity A. Estrogen receptor β suppresses metastasis of inflammatory breast cancer by regulating cell cytoskeleton and cytokine signaling [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-05-10.

Abstract P5-05-04: Myc as a poor prognostic marker for ER+ inflammatory breast cancer (IBC): Quantitative estrogen receptor (ER) expression analysis and gene expression analysis in ER+ IBC vs non-IBC

Background

Estrogen receptor-positive (ER+) primary inflammatory breast cancer (IBC) has a poorer prognosis than ER+ primary non-IBC. Our objective was to determine the association between ER positivity and survival outcome in order to elucidate the biological reason that ER+ IBC is more aggressive than non-IBC.

Methods

We retrospectively determined the relationship between ER expression by immunohistochemistry staining and neoadjuvant chemotherapy response as well as survival outcome for 189 patients with ER+ and HER2-negative (HER2-) IBC and 896 case-matched patients with stage III non-IBC seen at MD Anderson Cancer Center between January 1989 and April 2015. We performed gene expression (GE) analysis for 39 patients with ER+/HER2- IBC and 40 patients with non-IBC to detect genes that are specifically overexpressed in IBC. Logistic regression and Cox proportional hazards model were used to determine the predictive and prognostic value of percentages of cells positive for ER and progesterone receptor (PR) among the patients with ER+/HER2- IBC and non-IBC. Recursive partitioning analysis (RPA) was used to determine the optimal cutoff points for ER% and progesterone receptor (PR) % that maximized differences in survival. The identified cutoff points were tested in an external cohort of 192 ER+/HER2- IBC patients from Institut Paoli-Calmettes in France.

Results

The median values for ER% for IBC and non-IBC were 85 (range, 1-100) and 90 (range, 1-100), respectively. The logistic regression model demonstrated a lack of a relationship of ER% with pathological complete response rate to neoadjuvant chemotherapy both in IBC (P=0.29) and non-IBC (P=0.14). Expression of ER was significantly associated with distant disease-free survival (DDFS); hazard ratio (HR), 0.56 [95% CI, 0.37-0.83] per 50% increase in ER%; P&lt;0.05). Also, ER% was significantly associated with overall survival (OS) (HR, 0.40 [95% CI, 0.25-0.63] per 50% increase in ER%; P&lt;0.05). RPA showed that 91.5% and 9.0% were the optimal cutoff points for ER% and PR%, respectively, for DDFS and overall survival in IBC patients. However, the cutoff points could not be validated in the French external cohort. In the GE study, 84 genes were detected as significantly distinguishing ER+ IBC from non-IBC. Among the top 15 canonical pathways shown by IPA, the ERK/MAPK signaling pathway, PDGF pathway, insulin receptor signaling pathway, and IL-7 signaling pathway were associated with the ER signaling pathway. MYC upregulation was observed in three of these four pathways. Indeed, ER+/HER- IBC had significantly higher MYC amplification compared to those with non-IBC (P&lt;0.05) and higher MYC level was associated with poor relapse free survival for IBC (HR, 1.85 [95% CI, 1.05-2.70], P&lt;0.05).

Conclusions

Increased ER positivity was significantly associated with improved survival in ER+/HER- IBC patients. ER+/HER- IBC had several activated pathways with MYC upregulation compared to non-IBC. MYC upregulation was associated with a poor survival outcome for ER+/HER- IBC. The results indicate that MYC is a key gene for understanding the aggressive biological behavior of ER+/HER- IBC.

Citation Format: Iwase T, Harano K, Masuda H, Kida K, Espinosa Fernandez JR, Hess KR, Wang Y, Woodward WA, Layman RM, Dirix L, Van Laere SJ, Bertucci F, Ueno NT. Myc as a poor prognostic marker for ER+ inflammatory breast cancer (IBC): Quantitative estrogen receptor (ER) expression analysis and gene expression analysis in ER+ IBC vs non-IBC [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-05-04.

Abstract P1-18-04: CTCs and SUV to predict the efficacy of the bone-specific radiopharmaceutical agent radium-223 dichloride combined with hormonal therapy for hormone receptor-positive bone-dominant breast cancer metastasis

Background: Radium-223 dichloride (Ra-223) is a targeted alpha particle-based radiotherapeutic that has a localized cytotoxic effect on bone metastases. We sought to determine whether the circulating tumor cell (CTC) count and the presence of CTCs in epithelial-mesenchymal transition (EMT-CTCs) along with the standardized uptake value (SUV) on positron emission tomography-computed tomography (PET/CT) scans predict the efficacy of combined Ra-223 and hormonal therapy in patients with hormone receptor (HR)-positive bone-dominant metastatic breast cancer.

Patients and Methods: In this single-center phase 2 study (NCT02366130), 36 patients received Ra-223 (55 kBq/kg intravenously) on day 1 and then every 4 weeks for six cycles. Patients also received a standard care endocrine monotherapy. One non-bone metastatic site was allowed. The number of prior endocrine therapies was not limited and one prior chemotherapy was allowed for metastasis. Response was evaluated using the PET Response Criteria in Solid Tumors (PERCIST) with PET/CT at baseline, 6 and 9 months (mo) later. The CTC count (CellSearch) and the presence of EMT-CTCs (AdnaTest) was determined at baseline, 6 and 9 mo later. Progression-free survival (PFS) time was calculated to evaluate efficacy.

Results: Seven patients (20%) had a non-bone metastatic site. The median number of prior therapies for metastasis was 1 (range, 0-4). Six patients (17%) received chemotherapy. The median CTC count at baseline was 4 (range, 0-306). Only four patients (11%) were positive for EMT-CTCs at baseline. The median follow-up time was 14.7 mo (95% confidence interval [CI], 13.2 mo-not reached [NR]). The disease control rate at 9 mo was 46% in 33 patients who reached 9 mo or progressed up to 9 mo. The tumor response rate at 6 mo was 52% (complete/partialresponse rate; 22/30 %) in 27 patients whose disease was evaluable using PERCIST. The SUV on PET/CT decreased significantly at 6 and 9 mo after baseline (average decreases of 1.5 (p=0.0004) and 2.5 (p=0.0054), respectively). The median PFS duration was 7.4 mo (95% CI, 4.8 mo-NR). The median bone PFS was 16 mo (95% CI, 7.3 mo-NR). Patients with bone-only metastasis (N=28, 80%) had a significantly longer median PFS duration than did patients with non-bone metastases at baseline (N=7, 20%) (13.8 mo versus 4.5 mo; p=0.017). Patients without prior treatment (N=12, 34%) tended to have longer median PFS durations than did those who underwent prior treatment (N=23, 66%) (16.8 mo versus 4.8 mo; p=0.1865). Also, patients with &lt;5 CTCs at baseline (N=19, 54%) tended to have longer median PFS durations than did those with ≥5 CTCs (N=16, 46%) (13.8 mo versus 4.8 mo; p=0.1277). EMT-CTCs status did not predict efficacy.

Conclusions: Bone-only metastatic breast cancer and SUV suppression by Ra-223 are predictive of efficacy. Patients with baseline &lt;5 CTC count tended to have better outcomes than did those with ≥5 CTCs. Combined treatment with Ra-223 and a hormonal agent is especially effective at controlling bone metastasis in patients with HR-positive breast cancer. Bone-only metastatic disease and CTC count should be factored in future clinical trial designs.

Citation Format: Ueno NT, Tahara RK, Reuben JM, Gao H, Saigal B, Fujii T, Lucci A, Ibrahim NK, Damodaran S, Shen Y, Liu DD, Hortobagyi GN, Tripathy D, Lim B, Chasen BA. CTCs and SUV to predict the efficacy of the bone-specific radiopharmaceutical agent radium-223 dichloride combined with hormonal therapy for hormone receptor-positive bone-dominant breast cancer metastasis [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-18-04.

Abstract OT3-05-04: Phase II study of atezolizumab, cobimetinib, and eribulin in patients with recurrent or metastatic inflammatory breast cancer (IBC)

Background: IBCs that do not completely respond to chemotherapy often have dysregulated immune pathways, and novel therapies are needed to improve outcomes in recurrent/metastatic disease. One-third of IBCs express the atezolizumab target PD-L1, and cobimetinib increases PD-L1 expression; thus, we hypothesize that atezolizumab and cobimetinib may act synergistically in IBC. The FDA-approved agent eribulin is active in IBC and has anti-stem cell activity and can reverse the IBC phenotype of epithelial-to-mesenchymal transition. Hence the use of eribulin as a chemotherapy backbone in combination with other novel agents is well justified.

Trial Design: This single-arm, open-label trial is enrolling patients with recurrent IBC or de novo metastatic IBC that has progressed on at least 1 line of standard chemotherapy. During a 4-week pharmacodynamic window, patients have an upfront biopsy, receive atezolizumab and cobimetinib treatment for 4 weeks, and have a second biopsy. Triple-combination treatment then commences, with standard eribulin dosing. After 4 cycles of eribulin, patients receive maintenance targeted therapy until disease progression or intolerable toxicity.

Eligibility Criteria: Patients with metastatic IBC of any molecular subtype must have measurable disease (per RECIST 1.1) amenable to biopsy. Patients with HER2+ disease must have received both pertuzumab and T-DM1. Patients with treated stable brain metastases are allowed. Patients must have recovered from the acute effects of any prior therapies and have adequate hematologic, organ, and cardiac function. Patients with autoimmune diseases or a history of pneumonitis are ineligible.

Specific Aims: The primary objective is to determine the overall response rate (ORR) of the combination therapy. Secondary objectives include determining the safety and tolerability, clinical benefit rate, response duration, progression-free survival, 2-year overall survival rate and predictive biomarker analyses.

Statistical Methods: The trial will enroll up to 9 patients in its phase I/safety lead-in portion and up to 33 patients total. A Bayesian optimal interval design is used to efficiently determine the maximum tolerated cobimetinib dose in phase I. Patients start cobimetinib at the FDA-approved dose of 60 mg/day with a target toxicity rate is 0.3. Phase II will enroll 24 patients to determine the efficacy of the triple-combination therapy. The historical ORR in metastatic IBC is 10%; our sample size provides 80% power to detect an ORR improvement to 25%.

Accrual: The trial has enrolled 7 patients since its start in August 2017.

Citation Format: Alexander A, Marx AN, Reddy SM, Reuben JM, Le-Petross HC, Lane D, Huang ML, Krishnamurthy S, Gong Y, Gombos DS, Patel N, Tung CI, Allen RC, Kandl TJ, Wu J, Liu S, Patel AB, Futreal A, Wistuba I, Layman RM, Valero V, Tripathy D, Ueno NT, Lim B. Phase II study of atezolizumab, cobimetinib, and eribulin in patients with recurrent or metastatic inflammatory breast cancer (IBC) [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr OT3-05-04.

Abstract P2-06-22: PEA15-AA, an unphosphorylatable mutant of PEA15, as a novel therapeutic gene for triple-negative breast cancer

Background: Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer characterized by a high rate of metastatic recurrence and poor prognosis. Molecular mechanism underlying the metastatic behavior of TNBC has not been well elucidated, and newer approaches addressing drivers of metastasis are crucial to improving patient outcomes. PEA15 (Phosphoprotein enriched in astrocytes-15) regulates cell proliferation, apoptosis, and autophagy. In breast cancer, PEA15 expression inhibits invasion by binding to ERK and preventing its nuclear translocation. The biological function of PEA15 is tightly regulated by its phosphorylation at Ser104 and Ser116. However, the effect of PEA15 phosphorylation status on TNBC remains unknown. In this study, we tested the hypothesis that unphosphorylated PEA15 will prevent metastasis in TNBC through inhibition of the epithelial-to-mesenchymal transition (EMT).

Method: We established stable cells overexpressing unphosphorylatable (PEA15-AA) and phospho-mimetic (PEA15-DD) PEA15 mutants in MDA-MB-468 cells. To dissect specific Cellular Mechanisms regulated by PEA15 phosphorylation, we performed RT-PCR immune and metastasis arrays. In vivo mouse models were used to see effects of PEA15 phosphorylation on tumor growth.

Results: The clonogenic growth of PEA15-AA–expressing cells was significantly reduced by 80% compared with empty vector-transfected cells (PEA15-V). Anchorage-independent growth, an indicator of in vivo tumorigenicity, was inhibited in cells expressing PEA15-AA by 60% compared with PEA15-V. PEA15-AA upregulated the expression of E-cadherin and decreased the expression of mesenchymal markers, suggesting that PEA15-AA reverses EMT. Compared with PEA15-V, migration and invasion of cells expressing PEA15-AA were reduced by 65% and 72%, respectively. In contrast, PEA15-DD promoted migration, invasion, and expression of mesenchymal markers. To determine the in vivo effect of PEA15-AA, we injected stable PEA15 transfectants of MDA-MB-468 cells into the mammary fat pad of NOD/SCID mice. The PEA15-DD–injected group showed greater tumor volumes than PEA15-V and PEA15-AA groups, suggesting that PEA15-AA has antitumor effects both in vitro and in vivo. From the immune and metastasis arrays, we found that expression level of IL-8, which is known to induce EMT, was greatly decreased by PEA15-AA, while IL-8 was highly expressed in PEA15-DD cells. Addition of recombinant IL-8 to the cells expressing PEA15-AA partially rescued mesenchymal characteristics, increasing migration and expression of mesenchymal markers. By contrast, IL-8 knockdown in PEA15-DD–expressing cells decreased the mesenchymal phenotype. These findings indicate that IL-8 may play an important role as a mediator of phosphorylation of PEA-15 in breast cancer cell migration and invasion and suggest that PEA15-AA inhibits the expression of IL-8, thereby reversing EMT.

Conclusion: Taken together, our results show that PEA15 phosphorylation serves as an important regulator, having a dual role as an oncogene or tumor suppressor. Further studies are warranted to evaluate the impact of PEA15 phosphorylation status on metastasis in vivo. These findings support the development of PEA15-AA as a potential therapeutic strategy for TNBC.

Citation Format: Park J, Chauhan G, Cohen EN, Ueno NT, Battula VL, Tripathy D, Reuben JM, Bartholomeusz C. PEA15-AA, an unphosphorylatable mutant of PEA15, as a novel therapeutic gene for triple-negative breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-06-22.

Abstract OT2-07-09: A phase Ib study of neratinib, pertuzumab, and trastuzumab with paclitaxel in patients with metastatic and locally advanced breast cancer

Background: Neratinib, a potent irreversible pan-ErbB tyrosine kinase inhibitor that blocks signal transduction through HER1, HER2, and HER4, has demonstrated activity against metastatic HER2-positive breast cancer (HER2+ BC) in patients pretreated with trastuzumab. The FDA recently approved neratinib as an adjuvant treatment for HER2+ BC patients who have received trastuzumab for at least 1 year. Preclinical data demonstrate that trastuzumab-resistant BC cells remain sensitive to neratinib. Also, neratinib enhances responses to trastuzumab possibly by increasing trastuzumab's internalization, immune-mediated action, and other mechanisms. Taken together, these findings provide the rationale for adding neratinib to the standard of care combination of trastuzumab and pertuzumab with paclitaxel to enhance anti-HER2 efficacy in advanced HER2+ BC. Here, we report on the phase Ib portion of an ongoing phase Ib/II trial of this drug combination.

Trial Design: Patients with metastatic or locally advanced HER2+ BC will be enrolled in the phase Ib portion of the trial. Neratinib is given orally in 3-week cycles. The initial neratinib dose of 80 mg daily is increased to 120, 160, and 200 mg daily after safety assessments of each dose level. Other agents are administered as per the standard of care. Patients continue therapy with per-protocol dose escalation and de-escalation according to toxicity until the maximum tolerated dose (MTD) of neratinib is reached. The target maximum dose-limiting toxicity rate is 20%. All patients receive 4 cycles of the combination therapy. If patients do not have disease progression or excessive toxicity, they may receive 2-4 additional cycles at the treating physician's discretion. During therapy, patients undergo blood tests every week and have clinical visits and restaging scans every 3 weeks. Because gastrointestinal toxicity, mainly diarrhea, is anticipated, patients receive prophylactic antidiarrheal medication (e.g., loperamide, budesonide) beginning with the first dose of neratinib.

Eligibility Criteria: Eligible patients must have histologically confirmed metastatic or locally advanced HER2+ BC (BC may be inflammatory or non-inflammatory and have any hormone receptor status); an ECOG performance status score of 0 or 1; and adequate hematologic and organ function, including adequate cardiac function (as indicated by a left ventricle ejection fraction of ≥50%).

Specific Aims:

1- To determine the MTD of neratinib in combination with paclitaxel, pertuzumab, and trastuzumab.

2- Pharmacodynamic markers will be measured on biologic specimens. Neratinib-induced changes in pEGFR and/or HER2 expression will be analyzed and compared between dose levels.

Statistical Methods: The Bayesian modified toxicity probability interval is used to determine dose adjustment.

Accrual: The target enrollment for the phase Ib cohort is 20 patients. The trial has enrolled 3 patients since its activation in January 2018. This trial is supported by Puma Biotechnology, Aggressive Breast Cancer Research Program Grant.

Citation Format: Al-Awadhi A, Kono M, Marx A, Moseley T, Willey J, Sun H, Fu M, Whitman GJ, Valero V, Ueno NT, Lim B. A phase Ib study of neratinib, pertuzumab, and trastuzumab with paclitaxel in patients with metastatic and locally advanced breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr OT2-07-09.

Comparative efficacy of adjuvant trastuzumab-containing chemotherapies for patients with early HER2-positive primary breast cancer: a network meta-analysis

BACKGROUND

Trastuzumab (H) with chemotherapy benefits patients with HER2+ breast cancer (BC); however, we lack head-to-head pairwise assessment of survival or cardiotoxicity for specific combinations. We sought to identify optimal combinations.

METHODS

We searched PubMed, updated October 2017, using keywords "Breast Neoplasms/drug therapy," "Trastuzumab," and "Clinical Trial" and searched Cochrane Library. Our search included randomized trials of adjuvant H plus chemotherapy for early-stage HER2+ BC, and excluding trials of neoadjuvant therapy or without data to obtain hazard ratios (HRs) for outcomes. Following PRISMA guidelines, one investigator did initial search; two others independently confirmed and extracted information; and consensus with another investigator resolved disagreements. Before gathering data, we set outcomes of overall survival (OS), event-free survival (EFS), and severe cardiac adverse events (SCAEs). Analyzing 6 trials and 13,621 patients, we made direct and indirect comparisons using network meta-analysis on HR for OS or EFS and on odds ratio (OR) for SCAE; ranked therapy was done based on outcomes using p scores.

RESULTS

Compared with anthracycline-cyclophosphamide with taxane (ACT), ACT with concurrent H (ACT+H) showed best OS (HR 0.63, 95% confidence interval [CI] 0.55, 0.72), followed by taxane and carboplatin (TC) with concurrent H (TC+H) (HR 0.77, 95% CI 0.59, 1) and ACT with sequential H (ACT-H) (HR 0.85, 95% CI 0.68, 1.05). Pairwise comparisons showed statistically significant OS benefit for ACT+H over others; similar results for EFS. TC+H showed statistically significant lower SCAE risk compared to ACT+H (OR 0.13, 95% CI 0.03, 0.61).

CONCLUSIONS

Concurrent H with ACT or TC showed most clinical benefit for early-stage HER2+ BC; TC+H had lowest cardiotoxicity.

Revisiting the definition of estrogen receptor positivity in HER2-negative primary breast cancer

Background

Although 1% has been used as cut-off for estrogen receptor (ER) positivity, several studies have reported that tumors with ER < 1% have characteristics similar to those with 1% ≤ ER < 10%. We hypothesized that in patients with human epidermal growth factor 2 (HER2)-negative breast cancer, a cut-off of 10% is more useful than one of 1% in discriminating for both a better pathological complete response (pCR) rate to neoadjuvant chemotherapy and a better long-term outcome with adjuvant hormonal therapy. Our objectives were to identify a percentage of ER expression below which pCR was likely and to determine whether this cut-off value can identify patients who would benefit from adjuvant hormonal therapy.

Patients and methods

Patients with stage II or III HER2-negative primary breast cancer who received neoadjuvant chemotherapy followed by definitive surgery between June 1982 and June 2013 were included. Logistic regression models were used to assess the association between each variable and pCR. Cox models were used to analyze time to recurrence and overall survival. The recursive partitioning and regression trees method was used to calculate the cut-off value of ER expression.

Results

A total of 3055 patients were analyzed. Low percentage of ER was significantly associated with high pCR rate (OR = 0.99, 95% CI = 0.986-0.994, P < 0.001). The recommended cut-off of ER expression below which pCR was likely was 9.5%. Among patients with ER ≥ 10% tumors, but not those with 1%≤ER < 10% tumors, adjuvant hormonal therapy was significantly associated with long time to recurrence (HR = 0.24, 95% CI = 0.16-0.36, P < 0.001) and overall survival (HR = 0.32, 95% CI = 0.2-0.5, P < 0.001).

Conclusion

Stage II or III HER2-negative primary breast cancer with ER < 10% behaves clinically like triple-negative breast cancer in terms of pCR and survival outcomes and patients with such tumors may have a limited benefit from adjuvant hormonal therapy. It may be more clinically relevant to define triple-negative breast cancer as HER2-negative breast cancer with <10%, rather than <1%, of ER and/or progesterone receptor expression.

Abstract P1-01-09: BMP4 suppresses the progression of breast cancer through altered expression of metastasis regulating genes

Metastasis is a lethal manifestation of cancer, the development of which is the major cause of death in cancer patients. During a search for metastasis-regulating elements, an inverse correlation was identified between the in vivo tumor expression of bone morphogenetic protein-4 (BMP4) and spontaneous metastasis in a panel of isogenic mammary tumors of varying metastatic capacity. BMP4 is an essential morphogen in development, regulating cellular mechanisms akin to those in metastasis, including cellular differentiation, pluripotency and apoptosis. We therefore initiated an investigation of the impact of BMP4 expression on the metastatic process.

We studied the effect of enforced expression of BMP4 in a highly metastatic mammary tumour model called 4T1.2, comparing in vitro properties and tumour progression in mice. There were no differences in proliferation in vitro or when implanted into the mammary gland of immunocompetent mice. In contrast, mice bearing equivalent-sized 4T1.2-BMP4 tumors revealed dramatically reduced metastasis to lung, lymph node and bone. In a parallel study where the established orthotopic primary tumor was resected, survival was significantly extended in mice bearing 4T1.2-BMP4 tumors. Enforced BMP4 expression in tumor cells introduced intravenously resulted in a 2.5-fold decrease in lung metastatic burden, consistent with the impaired capacity of tumor cells to survive in circulation and colonize the lung. Conversely, silencing BMP4 expression in separate weakly metastatic tumours enhanced their ability to colonize the lung and shortened the survival of the mice. No changes were found in the ability of tumor cells expressing BMP4 or treated with recombinant BMP4 to migrate or invade through Matrigel in chemotactic assays but BMP4 enhanced anoikis in both mouse and human breast cancer cells, indicating that BMP4 sensitizes disseminated cells to anoikic stresses induced by cell-substrate detachment and shear flow during systemic transit. BMP4 activated canonical BMP-SMAD signaling in our mammary tumours, leading to altered expression of known metastasis-regulating genes, including SMAD7. SMAD7 depletion in metastasis-deficient 4T1.2-BMP4 tumors accelerated the onset of metastatic disease.

In a meta-analysis of 3,587 breast cancer patients in publically available datasets, low BMP4 mRNA expression was significantly associated with reduced relapse-free survival (RFS) (HR = 0.85, P = 0.01). In an independent analysis using the BreastMark algorithm, low levels of BMP4 mRNA were associated with reduced RFS (HR = 0.88, P = 0.035), distant metastasis-free survival (HR = 0.83, P = 0.035) and overall survival (HR = 0.78, P = 0.006). At the protein level, in a tissue microarray from 415 treatment naïve patients, improved overall survival was observed in multivariate analysis for both BMP4 (HR = 0.66, P = 0.037) and SMAD7 expression (HR = 0.64, P = 0.035) individually. Expression of both proteins compared to neither further improved OS (HR = 0.55, P = 0.005).

In summary, we found strong evidence that BMP4 is a metastasis suppressor correlating inversely with metastatic potential in preclinical breast cancer models and predicting improved relapse-free and overall survival in breast cancer patients.

Citation Format: Redfern AD, Eckhardt BL, Cao Y, Sloan EK, Parker BS, Loi S, Ueno NT, Lau PK, Latham B, Anderson RL. BMP4 suppresses the progression of breast cancer through altered expression of metastasis regulating genes [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P1-01-09.

Abstract OT1-02-01: A phase II study of anti-PD-1 (MK-3475) therapy in patients with metastatic inflammatory breast cancer (MIBC) or non-IBC triple negative breast cancer (non-IBC TNBC) who have achieved clinical response or stable disease to prior chemotherapy

Primary Objective: To assess the efficacy of MK-3475 as a single agent in patients with MIBC and non-IBC TNBC. The primary endpoint is disease control rate at the end of 4 months after receiving the treatment. We will also investigate the association between biomarkers in the peripheral blood and tumor tissue, safety and efficacy.

Background: The extensive invasion of lymphatic vessels by tumor emboli in patients with IBC suggests that the host immune surveillance system is suboptimal or that the tumor cells have decreased immunogenicity through immune editing to avoid detection by the host. In the immune-competent host, tumor cells must overcome both innate and adaptive immunologic defenses of the host. The PD-1 receptor-ligand interaction is a major pathway hijacked by tumors to suppress immune control. MK-3475 is a potent and highly selective humanized mAb designed to block the interaction between PD-1 and its ligands, PD-L1 and PD-L2. MK-3475 strongly enhances T lymphocyte immune responses in cultured blood cells from healthy human donors, cancer patients, and primates. Mouse anti-PD-1, as a monotherapy, demonstrated efficacy in several syngeneic mouse tumor models. To date, no specific targeted therapeutic options exist for the treatment of MIBC and TNBC. After patients achieving a clinical response to systemic therapy, the maintenance of disease control is not guaranteed. Further, our recent publication suggests that IBC has immune dysfunction. Chemotherapies can debulk the disease volume but cannot be used for maintenance due to their toxicities. Using an anti PD-1 monoclonal antibody is a promising approach for this patient population.

Study Design and Treatment Plan: This is a single arm phase II study. Up to 35 patients with HER2 negative MIBC or metastatic TN-IBC (MTNBC) who have achieved clinical response or stable disease after receiving any prior systemic therapy for metastatic/recurrent disease, and meet all other criteria will be eligible. Patients will receive MK-3475 200 mg IV every 3 weeks for up to 2 years.

Statistical Considerations: The trial will be conducted using Simon's optimal two-stage design and the rate of disease control will be estimated accordingly. It is assumed that the MK-3475 single agent will have a disease control rate of 30%. A disease control rate of 10% or lower will be considered treatment failure and the regimen will be rejected under this circumstance.

Status of the study:

Activation Date: June 2015. 13 patients have been enrolled. Enrollment continues.

Sponsor: Merck Sharp & Dohme Corp.

State of Texas appropriation for rare and aggressive breast cancer research.

Citation Format: Willey JS, Parker CA, Valero V, Lim B, Reuben JM, Krishnamurthy S, Gong Y, Scoggins ME, Dryden MJ, Liu DD, Woodward WA, Ueno NT. A phase II study of anti-PD-1 (MK-3475) therapy in patients with metastatic inflammatory breast cancer (MIBC) or non-IBC triple negative breast cancer (non-IBC TNBC) who have achieved clinical response or stable disease to prior chemotherapy [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr OT1-02-01.

Abstract P2-02-04: Circulating protein biomarker profile for inflammatory breast cancer using a multiplexed proximity extension assay

Background: Expression of cancer related genes and proteins in clinical specimens are the mainstay of personalized targeted therapy; however, a diagnostic signature for inflammatory breast cancer (IBC) remains elusive. In this study, we employed a blood-based, non-invasive, sensitive technology to map biomarkers in patients with IBC at the protein level. Proximity Extension Assay consists of a harmonious blending of immunoassay and PCR to amplify protein expression signal, thereby enabling multiplexing with small sample input (1 μl). Other multi-platform assays require a large amount of clinical material, multi-step sample processing and complicated data analysis.

Materials and methods: Serum samples (n= 159) from patients with primary IBC (IBC, n= 30), metastatic IBC (MIBC, n= 54), locally advanced breast cancer (LABC, n= 24) and metastatic breast cancer (MBC, n= 27) were prospectively collected from subjects prior to starting a new therapy (treatment naive) or a new line of therapy between 2009 and 2012. Sera from 24 healthy normal donors (HD) were included in the analysis for comparison. The samples were analyzed using two panels: Proseek Multiplex Oncology II and Proseek Multiplex Inflammation I (Olink Proteomics, Uppsala, Sweden) for simultaneous detection of 92 human protein biomarkers in each panel. In the assay, each protein biomarker is detected by a matched pair of antibodies coupled to unique DNA-tags. Upon binding to the proteins, the correctly hybridized DNA-tags form an amplicon that can be measured by PCR.For initial analysis, sample populations were compared using the Mann-Whitney-U test.

Results: In comparison with HD sera, sera of breast cancer patients had 41 proteins from the oncology panel and 28 from the inflammation panel that were significantly higher, whereas 5 from the inflammation panel were significantly lower. From the inflammation panel, 11 proteins (PD-L1, IL-2, IL-7, IL-18, uPA, CCL4, CCL23, CXCL9, CXCL10, CXCL11 and TNF-alpha) showed significant differential expression between IBC and non-IBC derived samples (irrespective of metastatic status); for each marker, levels were higher in IBC than in non-IBC. In contrast, 9 proteins from the oncology panel (CRNN, CTSV, ERBB4, FR-gamma, ITGAV, MIA, PODXL, SCF and SEZ6L) were differentially expressed; however, each of these proteins was higher in non-IBC than in IBC. Among the aforementioned proteins, CCL4, IL-2, IL-7, PD-L1, TNF-alpha, uPA, CRNN, CTSV, FR-gamma, ITGAV, MIA, SCF and SEZ6L did not differentiate cancer and HD, but were uniquely characteristic of the IBC vs non-IBC comparison.

Conclusion: These preliminary data suggest that it is possible to distinguish between cancer patients and healthy normal donors, and also to delineate between IBC and non-IBC patients based on expression of serum proteins. Validation of this serum protein signature is planned in a larger patient cohort.

Citation Format: Cohen EN, Jayachandran G, Gao H, Tin S, Alvarez RH, Valero V, Lim B, Woodward WA, Ueno NT, Reuben JM. Circulating protein biomarker profile for inflammatory breast cancer using a multiplexed proximity extension assay [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-02-04.

Abstract OT3-06-04: A randomized phase II study of neoadjuvant panitumumab /carboplatin/paclitaxel (PaCT) versus carboplatin/paclitaxel (CT) followed by adriamycin and cyclophosphamide (AC) for newly diagnosed primary triple-negative inflammatory breast cancer (TNIBC)

Primary Objective: To determine pathological complete response (pCR) rate in patients with primary TNIBC treated with PaCT in comparison with CT, followed by AC. To explore if the pCR rate correlates with reduced nodal expression status; and with arginine methylation status of epidermal growth factor receptor (EGFR). We will identify molecular biomarkers predictive of the pCR rate by analysis of multiplexed immunohistochemical (IHC) staining, identify molecular biomarkers predictive of the pCR rate by genomic and proteomic analysis, and determine whether the inhibition of the EGFR pathway down regulates the COX-2 pathway and mesenchymal marker.

Background: EGFR is overexpressed in triple negative breast cancer (TNBC) and inflammatory breast cancer (IBC). Therefore, EGFR targeted therapy may have a promising role in TNBC and IBC. A study showed that EGFR-targeted therapy may enhance the initial chemosensitivity of TNBC cells. Panitumumab blocks epidermal growth factor ligands and transforming growth factor EGFá (TGFá) binding to EGFR, inhibits tumor growth, and elicits both tumor regression and eradication of established tumors in murine xenograft tumor models. Panitumumab, a fully humanized anti-EGFR antibody, has been shown to be active in a breast cancer preclinical model using human breast cancer cell line MDA-MB-468, which has been shown to overexpress EGFR by both IHC and fluorescence in situ hybridization (FISH). Furthermore, EGFR tyrosine kinase inhibitors such as erlotinib have antitumor activity against human IBC cell lines. Thus, EGFR targeted therapy may have a promising role in TNBC and IBC.

Study Design: In this open label randomized phase II trial, up to 72 patients with primary IBC, have no HER2 overexpression, and have &lt;10% expression of ER and PgR, who also meet other criteria will be randomized to PaCT arm - receiving panitumumab single agent in window study and 4 cycles PaCT, or CT arm - receiving 4 cycles of CT. All patients will receive 4 cycles of AC before surgery.

Statistical Considerations: A sample size of 36 patients per arm will achieve 84% power to detect a difference of 0.24 in pCR rate between 0.2 in the CT arm and 0.44 in the PaCT arm with a type I error rate of 10% using one-sided Z test. Based on historical data, we expect that the pCR rate of a PaCT regimen to achieve 24% additional efficacy compared with the CT regimen.

Status of the study:

Activation date: Oct. 2016. So far 6 patients have been enrolled. Enrollment continues.

Sponsor: Amgen.

State of Texas appropriation for rare and aggressive breast cancer research.

NIH grant 1R01CA205043-01A1

Citation Format: Willey JS, Parker CA, Lim B, Valero V, Le-Petross HT, Krishnamurthy S, Woodward WA, Lucci A, Wood AL, Sun H, Babiera GV, Song J, Shen Y, Valero V, Wang X, Ueno NT. A randomized phase II study of neoadjuvant panitumumab /carboplatin/paclitaxel (PaCT) versus carboplatin/paclitaxel (CT) followed by adriamycin and cyclophosphamide (AC) for newly diagnosed primary triple-negative inflammatory breast cancer (TNIBC) [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr OT3-06-04.

Abstract OT1-01-05: A phase II study using talimogene laherparepvec as a single agent for inflammatory breast cancer or non-inflammatory breast cancer patients with inoperable local recurrence

Objective: The primary purpose of the study is to determine the local and systemic antitumor efficacy of talimogene laherparepvec in locally recurrent breast cancer patients with or without distant metastases, as evidenced by improved overall response rates. This will be the first study to use biopsy of distant disease to demonstrate whether systemic immune modulation has antitumor efficacy in breast cancer patients.

BACKGROUND: Patients with locally recurrent breast disease frequently undergo multimodal treatment at the first occurrence of breast cancer, and because local treatment modalities such as surgical intervention and radiation are difficult to add, they subsequently receive systemic therapy. Talimogene laherparepvec (T-VEC) was developed to eliminate solid tumors and has since been considered as a potential treatment option for body surface tumors. In addition to T-VECinjected area, this agent is capable of modifying the immune response with the potential of inhibiting distant metastases. Hence, locally recurrent breast disease could benefit from T-VECregardless of concomitant distant metastases, and may offer a new local treatment option.

Study Design and Treatment Plan: This is a single agent phase II study. Patients with breast cancer who have recurrence of chest wall disease with or without distant metastasis, have at least 1 injectable lesion ≥5 mm in longest diameter or multiple injectable lesions that in aggregate have a longest diameter of ≥ 5 mm, and meet inclusion and exclusion criteria will be eligible to participate in the study. Patient will receive T-VEC via intra-tumoral injection every 2 weeks after the first initial injection (3 weeks).

STATISTICAL METHODS:

Up to 35 patients will be enrolled in the study. The trial will be conducted using a two-stage design and the overall response rate will be estimated accordingly. It is assumed that the talimogene laherparepvec single agent will have a response rate of 20%. A response rate of 5% or lower will be considered treatment failure and the regimen will be rejected under this circumstance.

Status of the study:

Activation Date: Aug 2016. 6 patients have been treated. Enrollment continues.

Sponsor: Amgen

State of Texas appropriation for rare and aggressive breast cancer research.

Citation Format: Willey JS, Marx AN, Lim B, Ibrahim NK, Valero V, Mittendorf EA, Reuben JM, Le-Petross HT, Whitman GJ, Krishnamurthy S, Woodward WA, Lucci A, Liu DD, Shen Y, Ueno NT. A phase II study using talimogene laherparepvec as a single agent for inflammatory breast cancer or non-inflammatory breast cancer patients with inoperable local recurrence [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr OT1-01-05.

Abstract P1-10-09: EPHA2-targeting enhances eicosapentaenoic acid cytotoxicity against triple-negative inflammatory breast cancer via ABCA1 inhibition–mediated membrane rigidity

Background: Effective treatment options for triple-negative inflammatory breast cancer (TN-IBC), the most aggressive form of breast cancer, are currently lacking. We previously reported that mediators of inflammation promote the growth of TN-IBC xenografts. Eicosapentaenoic acid (EPA), an omega-3 fatty acid (fish oil) with anti-inflammatory properties, is an emerging FDA-approved therapeutic with a favorable toxicology profile. Here we aimed to develop a novel approach to enhance EPA efficacy against TN-IBC by identifying a kinase inhibitor that synergizes with EPA's antitumor activity.

Methods and Results: Using a high-throughput siRNA screen in the TN-IBC cell line SUM149PT, we identified inhibition of ephrin type-A receptor 2 (EPHA2), an oncogenic receptor tyrosine kinase, as a target that sensitizes TN-IBC cells to EPA therapy. To determine the clinical relevance of EPHA2, we investigated a meta-analysis of breast cancer mRNA expression data sets and found that high EPHA2 tumor expression, compared with low expressing, correlated significantly with poor overall survival in TN-IBC patients (P = 0.01), while not with other subtypes. Similar findings were observed in vitro, were EPHA2 protein and mRNA overexpression occurred predominantly in the TN subtypes among 49 and 51 breast cancer cell lines (63% and 47%, respectively), highlighting EPHA2 translational potential. Functional expression studies using proliferation and apoptosis assays in vitro, and xenografts in vivo, were performed in two EPHA2-expressing TN-IBC cell lines, SUM149PT and BCX010, to validate EPHA2 as a synergistic combinational target with EPA. EPHA2 gene silencing in combination with EPA significantly reduced cell growth, and enhanced apoptosis, compared with untreated and monotherapy in vitro (P &lt; 0.05), and in vivo (P &lt; 0.001). To translate our findings to the clinic, we validated dasatinib, an FDA-approved small molecule inhibitor of EPHA2, in combination to EPA to significantly enhance apoptosis of TN-IBC cells in vitro (P &lt; 0.05) and in vivo (P &lt; 0.05), compared with untreated and monotherapies. Using membrane fluidity assessment and cholesterol quantification we determined that apoptosis induction after combination therapy was due to increased membrane rigidity and cholesterol concentrations in the plasma membrane of TN-IBC cells (P &lt; 0.05, compared with monotherapies). Finally, we discovered by western blot and gain/loss-of-expression studies that combination therapy inhibited the cholesterol efflux protein ATP-binding cassette sub-family A member 1 (ABCA1), which plays a significant role mediating increased cellular cholesterol (P &lt; 0.05), cell membrane rigidity (P &lt; 0.05), and induction of apoptosis (P &lt; 0.05) in TN-IBC after EPA and EPHA2-targeting combination therapy.

Conclusions: This is the first study demonstrating that EPA can enhance conventional targeted therapy against breast cancer. Our study provides molecular and preclinical evidence to support the development of an EPA/EPHA2-inhibition–based phase I clinical trial for patients with EPHA2-positive TN-IBC; our study further suggests the use of EPHA2 and ABCA1 protein expression as biomarkers for patient selection and therapeutic response.

Citation Format: Torres-Adorno AM, Vitrac H, Qi Y, Tan L, Levental KR, Fan Y-Y, Yang P, Chapkin RS, Eckhardt BL, Ueno NT. EPHA2-targeting enhances eicosapentaenoic acid cytotoxicity against triple-negative inflammatory breast cancer via ABCA1 inhibition–mediated membrane rigidity [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P1-10-09.

Abstract OT1-02-05: A single arm phase II study of adjuvant anti-PD1 (pembrolizumab) in combination with hormonal therapy in patients with hormone receptor (HR)-positive localized inflammatory breast cancer (IBC) who did not achieve a pathological complete response (pCR) to neoadjuvant chemotherapy

Background: The pCR rate to conventional chemotherapy in hormone receptor positive IBC has historically been low (7.4% for HR+ HER2-, and 30% for HR+ HER2+), and despite the use of adjuvant endocrine therapy, the recurrence rate is still as high as 40%. To date, no targeted agent is proven to improve the efficacy of adjuvant endocrine therapy within the IBC population to improve this poor disease free survival (DFS). One plausible reason for the poor efficacy of endocrine therapy is a suppressed immune system, which allows tumor cells to avoid detection despite expression of potential immunogenic surface antigens.

Trial Design: This is a single arm trial that will enroll stage III HR+ IBC patients who have completed neoadjuvant therapy but had residual disease at mastectomy. Enrollment should be before or within 2 months of beginning endocrine therapy. Monitoring of DFS will be done with radiological imaging every 3 cycles (starting at cycle 4) as clinically indicated, per standard of care. Pembrolizumab is given on day 1 of each 21 day cycle for up to 2 years if the disease is controlled, and hormonal therapy will be administered per standard of care.

Eligibility Criteria: Clinical stage 3 IBC ER+/PR+ and HER2 negative patients who completed neoadjuvant chemotherapy and surgery with evidence of residual cancer in the breast or lymph nodes, but be clinically disease-free with good performance status at the start of study. Patients also must have adequate hematologic and organ function, and have recovered from the acute effects from prior treatments.

Specific Aims: The primary objective is to determine the disease free survival (DFS) at 2 years of patients with adjuvant therapy using Pembrolizumab in combination with standard adjuvant hormonal therapy. The secondary objective is to determine the safety and toxicity profile of this combination.

Statistical Methods: With a sample size of 37 patients, assuming that 80% are alive (20% increase from historical data) and disease-free at 2 years, and all patients are followed for &gt;2 years after enrollment with no dropout, a 95% confidence interval around the 2-year estimate of DFS will be generated. DFS will then be compared with the historical control rate of 60% by year 2 using a one-sided exponential MLE test.

Accrual: To date we have enrolled 3 patients since activation in January 2017, and the target enrollment is 37 patients.

Contact information: For more information or to refer a patient, please contact study coordinator, Angela Alexander - aalexand@mdanderson.org

Citation Format: Alexander A, Willey J, Sun H, Parker CA, Marx AN, Wood AL, Reddy SM, Reuben JM, Bassett RL, Le-Petross HT, Krishnamurthy S, Gong Y, Woodward WA, Valero V, Ueno NT, Lim B. A single arm phase II study of adjuvant anti-PD1 (pembrolizumab) in combination with hormonal therapy in patients with hormone receptor (HR)-positive localized inflammatory breast cancer (IBC) who did not achieve a pathological complete response (pCR) to neoadjuvant chemotherapy [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr OT1-02-05.

Abstract P1-16-02: Phase II study of the feasibility and safety of radium-223 dichloride in combination with hormonal therapy and denosumab for the treatment of patients with hormone receptor-positive breast cancer with bone-dominant metastasis

Background

Radium-223 dichloride (Ra-223) is a therapeutic alpha particle-emitting radiopharmaceutical compound which have antitumor effect targeted on bone metastases. Alpha particles induces double strand DNA breaks and localized cytotoxic effect to cancer cells with limiting harm on normal tissues. We are conducting a phase II clinical trial of combination of Ra-223, hormonal therapy, and denosumab treatment in patients with hormone receptor (HR)-positive bone-dominant metastatic breast cancer (NCT02366130). In this preliminary analysis of the study, we aimed to evaluate the feasibility and safety of this combination therapy.

Methods

This single-center phase II study seeks to determine the efficacy and safety of Ra-223 in combination with hormonal therapy and denosumab. Major eligibility criteria include HR-positive breast cancer with bone and/or marrow predominant metastases. Patients with two or more visceral metastases were not eligible. There was no limit in the number of prior hormonal therapies in the metastatic setting. Patients received Ra-223 injection (55 kBq/kg intravenously) on day 1 of the study and then every 4 weeks thereafter for 6 cycles. Patients were also administered a single hormonal agent (i.e., tamoxifen, aromatase inhibitor, or fulvestrant at standard doses) daily and denosumab (120 mg subcutaneously) every 4 weeks. For this analysis, adverse events (AEs) were summarized using descriptive statistics.

Results

A total of 25 patients were enrolled and 22 were evaluable between March 2015 and December 2016. Median age was 58.5 years (range 31-79), and 59% of patients were postmenopausal. ECOG performance status was 0 in 16 patients (73%), and 1 in six patients (27%). HER2/neu was positive in only one patient. Four patients (18%) were de novo metastasis, no patients had visceral metastasis, and multiple bone metastases in 20 patients (91%) vs. focal metastasis in 2 (9%). Median time from diagnosis of bone metastasis was 4.8 months (range 0.5-96.6). Prior therapy for metastatic disease consisted of hormonal therapy in 50% of the patients (eight patients with one line and three patients with two lines), chemotherapy (9%), palbociclib (14%), radiation to bone metastasis (50%), and bone-supportive therapy (27% with zoledronic acid, 27% with denosumab). The median number of cycles of Ra-223 administered was 6 (range 4-6).

The median follow-up time was 4 months (range 2-8). There were no grade 3 or 4 AEs. Major non-hematological grade 1 and 2 AEs were bone pain (77%), fatigue (45%), nausea (36%), diarrhea (32%), AST/ALT elevation (23%), hot flashes (23%), and headache (18%). The most common hematological AEs were grade 1 or 2 neutropenia (23%), anemia (14%), and thrombocytopenia (18%). There was no treatment delay or discontinuation due to AEs.

Conclusion

Our results suggest that the addition of Ra-223 to hormonal therapy and denosumab is a feasible and safe combination therapy in patients with HR-positive breast cancer with bone-dominant metastasis. We continue to enroll patients in the phase II trial to evaluate the efficacy of the treatment.

Citation Format: Tahara RK, Fujii T, Saigal B, Ibrahim NK, Damodaran S, Barcenas CH, Murray JL, Chasen BA, Shen Y, Liu DD, Hortobagyi GN, Tripathy D, Ueno NT. Phase II study of the feasibility and safety of radium-223 dichloride in combination with hormonal therapy and denosumab for the treatment of patients with hormone receptor-positive breast cancer with bone-dominant metastasis [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P1-16-02.

Abstract P1-05-03: JNK signaling regulates tumor cell–tumor-associated macrophage cross-talk in triple-negative breast cancer

Despite advances in our understanding of the molecular mechanisms underlying the aggressiveness of triple-negative breast cancer (TNBC), the contribution of tumor-associated macrophages (TAMs) to TNBC pathogenesis has not been therapeutically exploited. TAMs are the most abundant cell types in the tumor microenvironment (TME) and the key contributor to tumor progression and invasion. We have found that c-Jun NH2-terminal kinase (JNK), a member of the MAPK family and a major regulator of inflammation, contributes to TNBC tumorigenesis by promoting the cancer stem-like cell phenotype. However, whether the JNK pathway regulates TAMs and their cross-talk with tumor cells in TNBC remains unknown. Here, we tested the hypothesis that JNK signaling contributes to TNBC aggressiveness by promoting the tumor cell–TAM cross-talk that facilitates TNBC cell invasiveness.

We found that, among 80 patients with primary inflammatory breast cancer (IBC), TNBC tumors (n=18) had 2-fold more TAMs than non-TNBC tumors (n=62, P=0.05) and that high TAM counts were correlated with shorter disease-free survival of patients with IBC (P=0.05). Both JNK1 and c-Jun were highly activated in TAMs, and JNK-IN-8, a pan-inhibitor of JNK, suppressed c-Jun activation. JNK-IN-8 also increased expression of M1 macrophage markers (CD80 and HLA-DR) but reduced expression of TAM markers (CD163 and CD206), suggesting that JNK suppresses M1 macrophage differentiation but promotes TAM differentiation. Co-culture with TAMs significantly enhanced migration and invasion of HCC70 and MDA-MB-468 human and 4T1 murine TNBC cells. Similarly, an enhancement in TNBC cells migration and invasion was observed following culture with TAM-conditioned medium, suggesting that TAMs enhance TNBC cellular activities through paracrine signaling. In addition, inhibition of JNK signaling in TNBC cells or in TAMs by JNK-IN-8 significantly suppressed TAM-promoted enhancement of TNBC cell migration and invasion. These studies strongly suggest that JNK regulates M1/TAM differentiation and TNBC cell–TAM cross-talk. Furthermore, cytokine/chemokine profiling analysis showed that, of the identified molecules, MCP-1 (secreted by TAMs) and VEGF (secreted by TNBC cells) had the highest expression levels and that their expression was dramatically reduced following JNK-IN-8 treatment. Stimulation with recombinant VEGF increased proliferation of MDA-MB-468 cells, and stimulation with recombinant MCP-1 enhanced migration of the cells. These findings suggest that VEGF and MCP-1 are involved in JNK-mediated TNBC cell–TAM cross-talk.

Together, our results suggest that JNK signaling regulates tumor cell–TAM cross-talk through MCP-1– and/or VEGF-mediated paracrine signaling and that JNK is an important therapeutic target in TNBC. Further animal studies using JNK-knockout TNBC cells co-injected with TAMs are needed to confirm our in vitro findings.

Citation Format: Xie X, Otsuka S, Chu K, Lu AY, Tripathy D, Dalby KN, Hittelman WN, Van Laere S, Bartholomeusz C, Ueno NT. JNK signaling regulates tumor cell–tumor-associated macrophage cross-talk in triple-negative breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P1-05-03.

Abstract P1-16-04: Somatic mutations, clinicopathologic characteristics, and survival in patients with untreated breast cancer with bone-only and non-bone sites of first metastasis

Background: Bone is the most common site of metastasis of breast cancer, and bone metastasis is associated with a high rate of skeletal-related events, all of which contribute to decreased quality of life and poor outcomes. Biological mechanisms of metastasis to bone may be unique, and identification of distinct signaling pathways and somatic mutations may provide biological insight into or rational targets for treatment of and prevention of bone metastasis. The aims of this study were to compare and contrast somatic mutations, clinicopathologic characteristics, and survival in breast cancer patients with bone only versus non-bone as first metastatic site.

Methods: Tumor samples were collected from 389 patients who had metastasis and untreated primary breast cancer. In each sample, 46 or 50 cancer-related genes were selectively amplified and analyzed for mutations by AmpliSeq Ion Torrent next-generation sequencing. We used Fisher's exact test to identify somatic mutations associated with bone-only first metastasis and logistic regression models to identify differences in clinicopathologic characteristics, survival, and somatic mutations between patients with bone-only first metastasis and patients with first metastasis in non-bone sites only (“other-only first metastasis”).

Results: Among the 389 patients, the first metastasis was located in bone only in 72 patients (18.5%), non-bone sites only in 223 patients (57.3%), and both in 94 patients (24.2%). Of the cancer-related genes analyzed, the most commonly mutated were TP53 (N=103), PIK3CA (N=79), AKT (N=13), and PTEN (N=2). Compared to patients with other-only first metastasis, patients with bone-only first metastasis had higher rates of hormone-receptor-positive disease, non-triple-negative subtype, and low nuclear grade (grade 1 or 2) (all 3 comparisons, p&lt;0.001); had a lower ratio of cases of invasive ductal carcinoma to cases of invasive lobular carcinoma (p=0.002); and tended to have a higher 5-year overall survival (OS) rate (78.2% [95% confidence interval (CI), 68.6%-89.0%] vs 55.0% [95% CI, 48.1%-62.9%]; p=0.051). However, in the subgroup of patients with TP53 mutation and in the subgroup of patients with PIK3CA mutation, OS did not differ between patients with bone-only and other-only first metastasis (p=0.49 and p=0.68; respectively). In univariate analysis, the rate of TP53 mutation tended to be lower in patients with bone-only first metastasis than in those with other-only first metastasis (15.3% vs 29.1%; p=0.051). In multivariate analysis, TP53 mutation was not significantly associated with site of first metastasis (p=0.54) but was significantly associated with hormone-receptor-negative disease (p&lt;0.001).

Conclusions: We did not find associations between somatic mutations and bone-only first metastasis in patients with untreated breast cancer. Patients with bone-only first metastasis have longer OS than patients with other-only first metastasis. More comprehensive molecular analysis may be needed to further understand the factors associated with bone-only metastatic disease in breast cancer.

Citation Format: Kono M, Fujii T, Matsuda N, Harano K, Chen H, Wathoo C, Aron JY, Tripathy D, Meric-Bernstam F, Ueno NT. Somatic mutations, clinicopathologic characteristics, and survival in patients with untreated breast cancer with bone-only and non-bone sites of first metastasis [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P1-16-04.

Abstract P3-05-08: Lymphoid and myeloid cell characterization of inflammatory breast cancer tumor microenvironment and correlation to pathological complete response

Background: Inflammatory breast cancer (IBC) is an aggressive form of breast cancer with poor response rates to current chemotherapy regimens. With recent successes of immune targeted therapies in other solid tumors and a growing understanding of how the immune tumor microenvironment (TME) affects non-IBC outcomes, we sought to characterize the immune TME in IBC to identify biomarkers of treatment response and potential targets for drug development.

Methods: Pre-treatment core biopsy samples were identified from the MD Anderson Cancer Center IBC tissue bank from patients with stage III and de novo stage IV (with T4d) disease who received neoadjuvant chemotherapy (NAC) with intent to take to mastectomy. Lymphocytes were characterized by stromal tumor infiltrating lymphocyte (sTIL) quantification, CD8 T cell quantification, and T cell receptor sequencing. PD-L1 expression was assessed using DAKO 22C3 clone on tumor and immune cells. Myeloid cells were characterized using a multiplex immunohistochemistry approach, using CD68 and CD163 for macrophage markers, tryptase for mast cell marker, HLA-DR for class II antigen presentation marker, and cytokeratin as tumor marker. Spatial analyses were performed by determining probabilities of finding cell 1 of interest within 20 uM of cell 2 of interest and computing area under the curve for statistical comparison.

Results: 91 patients with stage III (N=62) or de novo stage IV (n=29) disease were identified. Breast cancer subtype included 25 triple negative, 34 HER2+ and 32 HER2-HR+. 86 patients received a mastectomy, of whom 33 (38.4%) patients experienced a pathologic complete response (pCR). sTIL was higher in stage III tumors (11.9 vs 4.8%, p&lt;0.001) and in those having a pCR (13.8 vs 7.3%, p=0.019). CD8 T cell density (available in 48 cases) similarly was higher in stage III patients (360.3 vs 178.8 counts/mm2, p=0.040) and pCR cases (452.3 vs 219.2 counts/mm2, p=0.080) but also higher in HER2+ disease (560.9 for HER2+ vs 239.9 counts/mm2, p=0.087 for TNBC and 153.6 counts/mm2, p=0.005 for HER2-HR+). T cell clonality (available in 32 cases) ranged from 0.004 to 0.242 but showed no correlation to tumor characteristics or response. PD-L1 complete tumor membranous expression was seen in only 1 of 47 cases, whereas PD-L1 positivity on immune cells was seen on 36.2% of cases; neither correlated to response. Myeloid cell assessment (available in 25 cases) showed higher mast cell infiltration in non-pCR cases (63.8 vs 26.8 counts/mm2, p=0.008) and spatial analysis (performed on 10 cases) identified that closer proximity of mast cells to CD8 T cells correlates with response (AUC 6.0 vs 2.2, p=0.017), suggesting a possible immunosuppressive mechanism. HLA-DR analysis demonstrated no difference by response as a single stain marker, but co-localization of HLA-DR with cell type shows higher HLA-DR expression on tumor cells in non-responders (14.6 vs 1.6%, p=0.031).

Conclusions: Higher TIL and CD8 T cell density are correlated with improved responses to NAC in IBC. Mast cell infiltration and HLA-DR expression on tumor cells are inversely correlated to response and suggest possible mechanisms of resistance. Mast cells could present potential therapeutic target in IBC.

Citation Format: Reddy SM, Reuben A, Jiang H, Roszik J, Tetzlaff MT, Reuben J, Wang L, Tsujikawa T, Barua S, Rao A, Villareal L, Wood A, Woodward W, Ueno NT, Krishnamurthy S, Wargo JA, Mittendorf EA. Lymphoid and myeloid cell characterization of inflammatory breast cancer tumor microenvironment and correlation to pathological complete response [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P3-05-08.

Abstract P3-09-05: Getting the most out of the 21-gene recurrence score assay: Increasing actionable results with a combined pathologic-genomic model

Introduction: The 21-gene recurrence score (RS) assay categorizes hormone receptor positive, node negative breast cancers (BC) into 3 risk groups for recurrence. We previously showed that the AAMC Model, using only standard pathology data, accurately does the same. This study compares the recurrence rate of the AAMC Model's risk groups to RS-based risk groups. A 2-step approach then is used, in which the AAMC model is applied first, and the RS assay is used only for AAMC intermediate risk cases. AAMC intermediate cases were reclassified by RS into low or high risk groups.

Methods: From a prospective registry of newly diagnosed BC, we selected invasive, hormone receptor positive, HER2 negative, lymph node negative cases from 2005 to 2015 tested with RS assay. Five-year Kaplan-Meier distant recurrence rates were calculated for each risk category.

Results: 1268 cases were included. Five-year recurrence rates were similar between the AAMC Model's low risk group and RS&lt;18 low risk group, as well as between the AAMC Model's high risk group and the RS&gt;30 high risk group. Applying the RS assay to the 715 cases in the AAMC Model's intermediate group resulted in re-classifying 417 (58%) as low risk and 41 (6%) as high risk. Using RS alone, 33% of cases were intermediate risk (n=424), whereas in the 2-step approach 20% were intermediate risk (n=257). For the 2-step approach, the 5-year distant recurrence rate was 3.3% for the low risk group (n=740) and 24.4% for the high risk group (n=271).

Conclusions: Five-year recurrence rates in the AAMC Model's low and high risk groups were similar to those in RS-based risk groups. The 2-step approach, with RS used only for AAMC intermediate cases, resulted in larger low and high risk groups with equivalent prognostic accuracy, compared to use of the RS assay alone. The 2-step approach reliably identifies a large number of patients unlikely to benefit from 21 gene assay and provides substantial cost savings.

Kaplan-Meier Calculated 5-year Distant Recurrences Rates for 4 Models: 1268 Patients Oncotype DXTAILORxAAMC Model2 Step Model with OncotypeDX for AAMC IntermediatesLow RiskRS &lt; 18 (n=703)RS &lt; 11 (n=250)Grade 1 and PR ≥ 1% (n=323)AAMC Low or AAMC intermediate/RS &lt;18 (n=740) 3.4% (95% CI 1.6 – 5.1%, nf=17)4.0% (95% CI 0.8 – 7.2%, nf=8)2.7% (95% CI 0.0 – 5.4%, nf=5)3.3% (95% CI 1.4 – 5.2%, nf=16)Intermediate RiskRS 18 - 30 (n=424)RS 11 - 25 (n=787)Not meeting AAMC definition for low or high risk (n=715)AAMC Intermediate and RS 18-30 (n=257) 15.2% (95% CI 10.3 – 20.1%, nf=38)7.3% (95% CI 4.7 – 9.9%, nf=35)8.4% (95% CI 5.4 – 11.3%, nf=36)12.0% (95% CI 5.8 – 18.1%, nf=15)High RiskRS &gt; 30 (n=141)RS &gt; 25 (n=231)Grade 3 or ER &lt; 20% (n=230)AAMC High or AAMC intermediate/RS &gt; 30 (n=271) 23.0% (95% CI 14.7 – 31.3%, nf=27)22.9% (95% CI 15.9 – 29.9%, nf=39)22.8% (95% CI 16.1 – 29.5%, nf=41)24.4% (95% CI 18.0 – 30.7%, nf=51)RS= Recurrence Score, nf=number of recurrences, CI = confidence interval.

Citation Format: Mylander C, Rosman M, Gage M, Fujii T, Le Du F, Raghavendra A, Sinha A, Espinosa Fernandez JR, James A, Ueno N, Tafra L, Jackson R. Getting the most out of the 21-gene recurrence score assay: Increasing actionable results with a combined pathologic-genomic model [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P3-09-05.

Abstract P3-07-04: EphA2: An emerging target in triple-negative breast cancer

Purpose: Breast tumors classified as 'triple negative' (TNBC) lack defining markers ER/PR/HER2 and do not have clinically-approved targeted therapy. This heterogeneous classification of breast cancers, while immediately responsive to standard chemotherapy, commonly develop resistance and have a poor five-year survival rate. As such, the identification of new therapeutic targets are warranted. As part of our drug discovery platform, we have identified EphA2, as a synthetic-lethal gene that enhances the therapeutic action of FDA-approved, anti-inflammatory compounds. Thus we sought to ascertain the relevance of EphA2-targeted therapy in TNBC, through the evaluation of the marker in preclinical and clinical specimens.

Methods: Sixty-one human and murine breast cancer cell lines or patient-derived xenografts were collated. Protein lysates were created from cells in vitro or from respective tumors established from cells implanted into NSG mice. Forty-nine tumors established (minimum 500mm3) and were surgically removed, fixed in formalin and paraffin embedded. A TMA was constructed with tumor specimens represented twice on the array and reflected all molecular subtypes including; ER-positive (n=5), PR-positive (n=3), HER2-positive (n=9) and TNBC (n=31). Immunostaining for EphA2 was performed with the rabbit monoclonal antibody EphA2 (D4A2) XP (Cell Signaling, #6997) using manufacturer's instructions. Immunostaining was evaluated using the H-score method (score between 0-300), with positive staining for EphA2 reflecting a score of 100 or greater. Analysis of breast cancer lysates by western blot was analyzed by absolute and relative quantitation methods; gene expression data was assessed through Oncomine or using the BreastMark algorithm (http://glados.ucd.ie/BreastMark/). This algorithm integrates gene expression and survival data from 26 datasets on 12 different microarray platforms corresponding to ˜17,000 genes in up to 4,738 samples.

Results: In an integrated gene expression platform (BreastMark), we observed that elevated EphA2 expression was associated with poor prognosis in a cohort of TNBC patient tumor samples. Western blot analysis of EphA2 protein on breast cancer cell lines, identified a greater percentage of TNBC cells expressing EphA2 compared to non-TNBC cell lines. EphA2 immunostaining was observed in the majority of tumor tissues. When present on cancer cells, EphA2 localized to the cell surface; while displaying ubiquitous localization within stromal populations. Cell surface expression of EphA2 on cancer cells was largely restricted to TNBC tumors (11/31 tumors, 35.5%) compared to other molecular subtypes (1/13 non-TNBC tumors, 7.7%; p = 0.0294). Expression of EphA2 in stromal cell populations was similar between groups (TNBC = 22/31, non-TNBC = 11/13; p = 0.1711).

Conclusions: Our analysis determined that EphA2 was specifically expressed on cancer cells derived from tumors with a 'triple-negative' molecular subtype. Collectively our data suggests that EphA2 is an emerging target in TNBC and that therapies directed against EphA2 may provide a significant benefit for a majority of patients that express this marker.

Citation Format: Eckhardt BL, Torres AM, Woodward WA, Krishnamurthy S, Meric-Bernstam F, Ueno NT. EphA2: An emerging target in triple-negative breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P3-07-04.

Abstract P5-21-15: The synergistic antitumor activity of entinostat (MS-275) in combination with palbociclib (PD 0332991) in estrogen receptor-positive and triple-negative breast cancer

BACKGROUND: CDK4/6 regulates the G1-S phase transition by phosphorylating the retinoblastoma protein (Rb). Given their potent clinical efficacy, CDK4/6 inhibitors used in combination with hormone receptor (HR) blockade (with an aromatase inhibitor or fulvestrant) are emerging as the standard of care for patients with metastatic HR-positive breast cancers. The CDK4/6 inhibitors palbociclib and ribociclib are FDA-approved for use in HR-positive breast cancer patients, and abemaciclib is currently in phase III trials. We observed that approximately 74% (25/34) of breast cancer cell lines had high phosphorylated Rb (phospho-Rb) expression levels and that triple-negative breast cancer (TNBC) cell lines often expressed phospho-Rb, suggesting that targeting phospho-Rb via CDK4/6 inhibition may be effective against TNBC. The histone deacetylase (HDAC) inhibitors increase p21Cip1 levels, promoting proteasomal degradation of cyclin B1 and resulting in G2/M arrest. Entinostat is an oral, class 1, selective HDAC inhibitor currently in phase III testing in HR-positive breast cancer. Preclinical and clinical data demonstrate that entinostat, in combination with HR blockade, has anticancer activity. Our group recently reported that entinostat combined with other anticancer drugs induced apoptosis via induction of proapoptotic proteins such as Noxa and Bim in breast cancer cell lines. Based on these findings, we hypothesized that entinostat-induced apoptosis and palbociclib-induced cell cycle arrest synergize to produce enhanced antitumor effects in estrogen receptor (ER)-positive breast cancer and TNBC cell lines with high phospho-Rb expression levels.

METHODS: We assessed the combination antitumor effects and their mechanisms via CellTiter Blue and sulforhodamine B assays, flow cytometry, apoptosis (caspase 3/7) assays, anchorage-independent growth assays, Western blotting, reverse phase protein array (RPPA), and mammary fat pad xenograft mouse models.

RESULTS: RPPA data showed that ER-positive and TNBC cell lines more often expressed phospho-Rb than did other breast cancer cell subtypes (7/10 and 8/17 cell lines, respectively). We found that the combination of entinostat and palbociclib synergistically inhibited tumor cell proliferation (combinational index less than 1.0), reduced in vitro colony formation (P &lt; 0.05), inhibited in vivo tumor growth in ER-positive MCF-7 breast cancer cells (P &lt; 0.05), and inhibited tumor growth in TNBC xenograft mouse models (MDA-MB-231) more effectively than did either drug alone.

CONCLUSION: Taken together, our data provide evidence that combining entinostat with palbociclib enhances the antitumor effects of these drugs. Along with our continued effort to determine predictive biomarkers, our findings justify conducting a clinical trial of combination treatment with entinostat and palbociclib in patients with ER-positive breast cancer or TNBC.

Citation Format: Lee J, Lim B, Pearson T, Tripathy D, Ordentlich P, Ueno NT. The synergistic antitumor activity of entinostat (MS-275) in combination with palbociclib (PD 0332991) in estrogen receptor-positive and triple-negative breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P5-21-15.

Abstract P6-03-05: Risk of needle-track seeding with serial ultrasound guided biopsies in triple negative breast cancer

Background: Image-guided percutaneous needle biopsy of the breast is a common procedure. In breast cancer patients (pts) undergoing core biopsies and surgical resection on the same day, the rate of tumor cell displacement along the needle track has been reported to be up to 50%. However, the clinical significance of this finding in triple negative breast cancer (TNBC) patients (pts) undergoing serial biopsies while receiving neoadjuvant chemotherapy (NACT) is unknown. Here we report the incidence of needle-track seeding (NTS) in a cohort of TNBC pts enrolled on a molecular triaging protocol involving serial biopsies of the index breast lesion.

Methods: We reviewed the clinical records of 144 consecutive TNBC pts enrolled on a molecular triaging protocol at MD Anderson Cancer Center. Per protocol, all pts underwent a pre-treatment research biopsy and were initiated on anthracycline based NACT (AC). Pts with inadequate response to front-line NACT were encouraged to undergo additional biopsies of the index breast lesion prior to switching therapies. Serial breast ultrasound (US) was performed to monitor therapeutic response and incidental evidence of needle-track seeding noted on US was documented.

Results: Clinicopathological characteristics of the pts are summarized in Table 1. 89% (128/144) of pts had a diagnostic breast biopsy done at another center prior to presenting at MDACC. To date, we have performed 209 US guided biopsies of index breast lesions in 144 pts. 92% (193/209) of these biopsies were done mainly for research purposes. 1.4% (2/144) of pts were found to have evidence of NTS on follow up US. The first pt had a T1N0 (1.9cm), grade 3, invasive ductal carcinoma (IDC) at diagnosis. She underwent a diagnostic biopsy followed by a research biopsy before initiating AC. She was found to have NTS as well as progression of disease (PD) on follow up US after 2 cycles of AC. The second pt had a T2N0 (3cm), grade 3 IDC at diagnosis. She underwent a diagnostic biopsy at another center, followed by a research biopsy before initiating AC. Like the first pt, she was found to have NTS and PD on follow up US after 2 cycles of AC. Both pts are currently on neoadjuvant clinical trials of novel agents.

Conclusion: The rate of NTS detected on US in TNBC pts undergoing serial biopsies of index breast lesions while receiving NACT is low and further studies are needed to determine the impact of serial biopsies on long term outcomes in TNBC.

Table 1: Patient CharacteristicsCharacteristicN=144Age - Median (years, interquartile range)55 (46-62)Tumor Size Mean (cm, standard deviation)3.4 (2.2)T1 – n(%)35 (24)T2 – n(%)89 (62)T3 – n(%)19 (13)T4 – n(%)1 (1)Clinical Nodal Status Negative – n(%)74 (51)Positive – n(%)70 (49)Grade 1 – n(%)1 (1)2 – n(%)17 (12)3 – n(%)124 (86)Unknown – n(%)2 (1)Histologic Subtype Invasive ductal carcinoma – n(%)121 (84)Invasive lobular carcinoma – n(%)2 (1)Mixed ductal and lobular carcinoma – n(%)3 (2)Metaplastic carcinoma – n(%)13 (9)Not specified – n(%)5 (3)Laterality Right – n(%)72 (50)Left – n(%)72 (50)

Citation Format: Yam C, Santiago L, Candelaria RP, Adrada BE, Rauch GM, Hess KR, Litton JK, Piwnica-Worms H, Mittendorf EA, Ueno NT, Lim B, Murthy RK, Damodaran S, Helgason T, Huo L, Thompson AM, Gilcrease MZ, Symmans WF, Moulder SL, Yang W. Risk of needle-track seeding with serial ultrasound guided biopsies in triple negative breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P6-03-05.

Abstract P4-14-02: CSF1/CSF1R axis reprograms epithelial-to-mesenchymal phenotypes in inflammatory breast cancer

Inflammatory breast cancer (IBC) accounts for 2% of breast cancers but 10% of breast cancer-related deaths in the US. Clinical hallmarks of IBC are tumor cell emboli in lymphatic vessels and overexpression of E-cadherin, which promotes cell clustering. Given these hallmarks, IBC is thought to spread via collective invasion and cell clusters. However, we showed that IBC cells underwent epithelial-to-mesenchymal transition (EMT) and metastasized through EMT. Thus, there are two contradictory theories of IBC metastasis. The objectives of this study were 1) to propose a model that reconciles these two models, and 2) to identify target molecules for inhibition of IBC metastasis. Methods: We previously showed that Matrigel culture induced EMT-like changes in SUM149 IBC cells. To test if this transformation from epithelial (E) to mesenchymal (M) in Matrigel culture is unique to IBC cells, a panel of breast cancer cells was cultured in both monolayer and Matrigel-coated plates. The cells were IBC (SUM149, SUM190, KPL4, IBC3), triple-negative breast cancer (TNBC) (MDA-MB-231, MDA-MB-468), and ER+ (MCF7) cells. Phenotypic changes in morphology and expression of EMT markers (E-cadherin, vimentin) were captured with bright field and immunofluorescent (IF) images, respectively. For genome-wide and targeted transcriptional analysis, SUM149 cells cultured in monolayer and Matrigel were processed using DNA microarrays and Taqman qRT-PCR. To correlate the Matrigel gene signature with M features in human breast cancer, a human breast cancer data set was hierarchically clustered with the Matrigel gene signature. Results: SUM149 cells showed a remarkable phenotypic change from E in monolayer culture to M in Matrigel. IF analysis confirmed induction of vimentin expression in Matrigel but stable expression of E-cadherin (thus, we refer to this state as E/M hybrid). This trend was also observed with SUM190 cells. Using qRT-PCR, we confirmed downregulation of E-cadherin and upregulation of M markers (vimentin, Twist1, Snail1, ZEB2) in Matrigel-cultured SUM149 and SUM190 cells compared to monolayer-cultured cells. DNA microarray transcriptional analysis confirmed this trend in SUM149 cells. TNBC has more M-like features than other breast cancer subtypes. Given this evidence, we clustered human breast cancer data using overexpressed genes in Matrigel-cultured SUM149 cells. We identified a cluster of 20 genes in TNBC samples and, assuming that these genes are drivers of E to E/M transition, chose the inflammation-related gene CSF1 as a candidate. The CSF1/CSF1R axis was inhibited by a CSF1R inhibitor, BLZ945; moreover, treatment with BLZ945 reversed the EMT changes in cells in Matrigel culture. Treatment with 5 μM BLZ945 re-induced E-cadherin expression and suppressed Snail1 and Twist1 expression in Matrigel-cultured SUM149 cells. Conclusion: IBC cells are more prone to undergo transition from E to E/M phenotype in Matrigel culture than are cells of other breast cancer subtypes. The CSF1/CSF1R axis plays a role in this E to E/M transition, thus warranting testing its significance using an in vivo IBC model. Phenotypic transition and reversion between E and E/M phenotypes could be a new paradigm that reconciles two contradictory models of IBC metastasis.

Citation Format: Kai K, Iwamoto T, Zhang D, Rao AUK, Thompson A, Sen S, Ueno NT. CSF1/CSF1R axis reprograms epithelial-to-mesenchymal phenotypes in inflammatory breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P4-14-02.

Abstract P1-07-22: Androgen receptor positivity is associated with nodal disease in triple negative breast cancer

Background: Gene expression profiling (GEP) has identified several molecularly distinct subtypes of triple negative breast cancer (TNBC). Currently, GEP-based molecular diagnostics are not routinely used in clinical decision making due to the lack of proven benefit, costs involved and long turnaround time. However, two molecularly distinct subtypes of TNBC, the luminal androgen receptor (AR) and mesenchymal subtypes, have surrogate CLIA-certified immunohistochemical (IHC) markers, AR and vimentin (VM), respectively, which have the potential for application in the clinic. Here we report the rates of AR and VM positivity and their association with clinicopathological characteristics in a cohort of TNBC pts receiving NACT.

Methods: As part of an ongoing molecular triaging protocol, 144 pts with stage I-III TNBC underwent a pretreatment biopsy for molecular characterization (MC) prior to initiating neoadjuvant chemotherapy (NACT). IHC for AR and VM were performed using commercially available antibodies. AR+ and VM+ were defined as ≥10% and ≥50% staining, respectively. Pts were randomized 2:1 to know (intervention arm, n=93) and not know (control arm, n=51) the MC results. The charts of pts randomized to the intervention arm were reviewed. Categorical variables were analyzed using Fisher's exact test. Ordinal and continuous variables were analyzed using the Wilcoxon rank-sum test and Student's t test as appropriate.

Results: 31% (29/93) and 16% (15/93) of pts were AR+ and VM+, respectively. Only 4% (4/93) of pts were both AR+ and VM+. Clinicopathological characteristics are summarized in Table 1. AR+ pts were more likely to have clinically node positive disease as compared to AR- pts (66% vs 34%, p=0.007). There were no significant differences in clinical tumor size or grade between AR+ and AR- pts. VM+ and VM- pts had similar clinicopathological characteristics.

Conclusion: Pts with AR+ TNBC were more likely to have node positive disease. The impact of AR+ on long term outcomes should be investigated in prospective studies.

Table 1: Association between patient characteristics and AR/VM status AR  VM   AR+ (n=29)AR- (n=64)p-valueVM+ (n=15)VM- (n=78)p-valueAge - Median (years, interquartile range)58 (48-65)52 (46-61)0.05855 (48-64)56 (47-62)0.88Clinical Tumor Size      Mean (cm, standard deviation)3.5 (1.8)3.0 (1.8)0.2872.7 (1.7)3.3 (1.9)0.31T1 – n(%)5 (17)21 (33)0.2307 (47)19 (24)0.098T2 – n(%)21 (72)36 (56) 7 (47)50 (64) T3 – n(%)3 (10)7 (11) 1 (7)9 (12) Clinical Nodal Status      Negative – n(%)10 (34)42 (66)0.0078 (53)44 (56)1.00Positive – n(%)19 (66)22 (34) 7 (47)34 (44) Grade      2 – n(%)6 (21)5 (8)0.0763 (20)8 (10)0.293 – n(%)23 (79)59 (92) 12 (80)70 (90) 

Citation Format: Yam C, Huo L, Hess KR, Litton JK, Yang W, Piwnica-Worms H, Mittendorf EA, Ueno NT, Lim B, Murthy RK, Damodaran S, Helgason T, Thompson AM, Santiago L, Candelaria RP, Rauch GM, Adrada BE, Symmans WF, Gilcrease MZ, Moulder SL. Androgen receptor positivity is associated with nodal disease in triple negative breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P1-07-22.

Hole-phonon coupling effect on the band dispersion of organic molecular semiconductors

The dynamic interaction between the traveling charges and the molecular vibrations is critical for the charge transport in organic semiconductors. However, a direct evidence of the expected impact of the charge-phonon coupling on the band dispersion of organic semiconductors is yet to be provided. Here, we report on the electronic properties of rubrene single crystal as investigated by angle resolved ultraviolet photoelectron spectroscopy. A gap opening and kink-like features in the rubrene electronic band dispersion are observed. In particular, the latter results in a large enhancement of the hole effective mass (> 1.4), well above the limit of the theoretical estimations. The results are consistent with the expected modifications of the band structures in organic semiconductors as introduced by hole-phonon coupling effects and represent an important experimental step toward the understanding of the charge localization phenomena in organic materials.The charge transport properties in organic semiconductors are affected by the impact of molecular vibrations, yet it has been challenging to quantify them to date. Here, Bussolotti et al. provide direct experimental evidence on the band dispersion modified by molecular vibrations in a rubrene single crystal.

Receptor clustering and activation by multivalent interaction through recognition peptides presented on exosomes

We demonstrate a novel system for inducing clustering of cell surface receptors via recognition peptide segments displayed on exosomes, leading to receptor activation. With this system, targeting of receptor-expressing cells and facilitation of the endocytic uptake of exosomes, which contained the anti-cancer protein saporin, were successfully achieved, leading to cell death.

PU.1 acts as tumor suppressor for myeloma cells through direct transcriptional repression of IRF4

We previously reported that PU.1 is downregulated in the majority of myeloma cell lines and primary myeloma cells of certain myeloma patients, and conditional expression of PU.1 in such myeloma cell lines induced cell cycle arrest and apoptosis. We found downregulation of IRF4 protein in the U266 myeloma cell line following induction of PU.1. Previous studies reported that knockdown of IRF4 in myeloma cell lines induces apoptosis, prompting us to further investigate the role of IRF4 downregulation in PU.1-induced cell cycle arrest and apoptosis in myeloma cells. PU.1 induced downregulation of IRF4 at the protein level, cell cycle arrest and apoptosis in six myeloma cell lines. Chromatin immunoprecipitation (ChIP) revealed that PU.1 directly binds to the IRF4 promoter, whereas a reporter assay showed that PU.1 may suppress IRF4 promoter activity. Stable expression of IRF4 in myeloma cells expressing PU.1 partially rescued the cells from apoptosis induced by PU.1. As it was reported that IRF4 directly binds to the IRF7 promoter and downregulates its expression in activated B cell-like subtype of diffuse large B cell lymphoma cells, we performed ChIP assays and found that IRF4 directly binds the IRF7 promoter in myeloma cells. It is known that IRF7 positively upregulates interferon-β (IFNβ) and induces apoptosis in many cell types. Binding of IRF4 to the IRF7 promoter decreased following PU.1 induction, accompanied by downregulation of IRF4 protein expression. Knockdown of IRF7 protected PU.1-expressing myeloma cells from apoptosis. Furthermore, IFNβ, which is a downstream target of IRF7, was upregulated in myeloma cells along with IRF7 after PU.1 induction. Finally, we evaluated the mRNA expression levels of PU.1, IRF4 and IRF7 in primary myeloma cells from patients and found that PU.1 and IRF7 were strongly downregulated in contrast to the high expression levels of IRF4. These data strongly suggest that PU.1-induced apoptosis in myeloma cells is associated with IRF4 downregulation and subsequent IRF7 upregulation.

Abstract P1-07-14: Rates of immune infiltration in patients with triple-negative breast cancers by molecular subtype and in patients with inflammatory and non-inflammatory breast cancers

Background

In patients with triple-negative breast cancer (TNBC), tumor-infiltrating lymphocytes (TILs) have been reported to be associated with improved survival. Lehmann et al. identified 6 molecular subtypes of TNBC [basal-like (BL) 1, BL2, mesenchymal (M), mesenchymal stem like (MSL), immunomodulatory (IM), and luminal androgen receptor (LAR)], and we previously reported that TNBC subtype is a predictor of pathologic complete response (pCR). Recently, the IM gene expression signature has been shown to be indicative of the presence of TILs and has been incorporated into TNBC subtyping as a modifier of the other groups rather than a separate subtype. However, the association between TNBC subtype and the presence of TILs is not known. We hypothesized that the BL2 and LAR subtypes, which have low pCR rates, have low rates of immune infiltration. Inflammatory breast cancer (IBC) is an aggressive cancer that is frequently triple-negative. The association between IBC and the presence of TILs also is not known. In this study, we analyzed the association between TNBC molecular subtype and the IM signature and determined whether the IM signature differed between patients with IBC and non-IBC.

Methods

We retrospectively analyzed 88 patients with TNBC from the World IBC Consortium dataset for whom IBC status was known (IBC, n=39; non-IBC, n=49) and tumor gene expression data were available. TNBC specimens were classified using the TNBCtype algorithm (Insight Genetics, Inc., TN, USA), which uses a 101-gene signature. For each tumor, the TNBCtype algorithm reports the TNBC molecular subtype (BL1, BL2, M, MSL, or LAR) and the IM status, which is described as positive (IM+) or negative (IM-). Recently, Fisher's exact test was used to analyze differences in subtype distribution between the IM+ and IM- tumors.

Results

The subtype distribution differed significantly between the IM+ and IM- tumors

IM signature in TNBC subtypesSubtypeTotal (n=88)IM+ (n=32)IM- (n=56)BL13015 (50)15 (50)BL2202 (100)M808 (100)MSL3113 (42)18 (58)LAR121 (8)11 (92)Not determined53 (60)2 (40) (p=0.0087). The majority of IM+ cases occurred in the BL1 and MSL subtypes. No IM+ cases were observed in the BL2 or M subtypes, and only 1 was observed in the LAR subtype. IM+ cases occurred at roughly the same frequency in patients with IBC (33%) and non-IBC (37%, p=0.73).

Conclusions

TNBC molecular subtypes differ in their degree of immune infiltration, and most IM+ TNBCs are of the BL1 and MSL subtypes. Our finding that the proportion of IM+ cases was not different between IBC and non-IBC indicates that TILs are recruited to the tumor microenvironment similarly in IBC and non-IBC tumors. Further, Pietenpol et al recently showed that the MSL signature represents normal stromal cells rather than tumor cells by performing laser-capture microdissection of TNBC specimen. Validation studies are needed to corroborate and further expand upon our findings.

Citation Format: Harano K, Wang Y, Lim B, Seitz RS, Morris SW, Bailey DB, Hout DR, Skelton RL, Ring BZ, Masuda H, Rao AUK, Woodward WA, Reuben JM, Ueno NT. Rates of immune infiltration in patients with triple-negative breast cancers by molecular subtype and in patients with inflammatory and non-inflammatory breast cancers [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P1-07-14.

Abstract OT2-01-22: NCT02456857: A phase II trial of liposomal doxorubicin, bevacizumab and everolimus (DAE) in patients (pts) with localized triple-negative breast cancer (TNBC) with tumors predicted insensitive to standard neoadjuvant chemotherapy (NACT)

BACKGROUND: Approximately 50% of TNBC pts treated with standard taxane/anthracycline-based NACT will have chemo-insensitive disease (CID) manifested as extensive residual disease (RCB-II or III) at the time of surgery. 40-80% of these pts will develop recurrence within 3 years of initial diagnosis. Recent advances in molecular profiling have identified subsets of TNBC with distinct, targetable molecular features. We developed a clinical trial to identify and characterize CID (ARTEMIS: A Randomized, TNBC Enrolling trial to confirm Molecular profiling Improves Survival). In the ARTEMIS trial, treatment naïve pts with localized TNBC undergo a pretreatment biopsy and then immediately start their initial phase of anthracycline-based chemotherapy so that the results of the molecular characterization are used in combination with response assessment (clinical exam/diagnostic imaging) to identify CID and inform the second phase of NACT, thus using a 'second hit' strategy in the middle of NACT to overcome drug resistance. The mesenchymal subtypes of TNBC have a high incidence of PI3K pathway activation. Preclinical models demonstrated response to PI3K inhibitors in this subtype. Metaplastic breast cancers make up ∼30% of tumors characterized as 'claudin-low/mesenchymal' by gene signature and are also associated with a high rate of PI3K activating molecular aberrations. A combination regimen of liposomal doxorubicin, bevacizumab and the mTOR inhibitors temsirolimus or everolimus (DAT or DAE) demonstrated response (including durable complete responses) in metastatic metaplastic breast cancer.

PRIMARY OBJECTIVE: Determine the rate of pathologic complete response (pCR/RCB-0) or minimal residual disease (RCB-I) after 4 cycles of DAE for treatment of mesenchymal TNBC deemed to be CID through the ARTEMIS trial

TRIAL DESIGN AND STATISTICAL METHODS: Only pts deemed to have mesenchymal CID on the ARTEMIS trial can enter this non-randomized phase II study. Realizing that pts without response to their initial cycles of chemotherapy have very low chance (5%) of achieving pCR with additional cycles of chemotherapy, it would be clinically meaningful to see pCR in this pt population improved to 20%. Counting pCR (RCB-0) or RCB-I as response, a two-stage Gehan-type design will be employed with 14 pts in the first stage. If at least one pt responds, 23 more pts will be added for a total of 37 pts. This design has a 49% chance of terminating after the first stage if the true response rate is 0.05, 23% chance if the true rate is 0.10, 10% if the true rate is 0.15 and 4% if the true rate is 0.20. If accrual continues to the second stage and a total of 37 pts are enrolled, the 95% confidence interval for a 0.20 response rate will extend from 0.10 to 0.35.

BRIEF ELIGIBILITY CRITERIA: Inclusion: localized TNBC enrolled onto ARTEMIS trial, adequate organ, bone marrow and cardiac parameters Exclusion: metastatic disease, pregnant or lactating pts, medical illness that increases chance of moderate to severe toxicity

CORRELATIVE SCIENCE: Correlate vimentin expression by IHC, mesenchymal signatures and PI3K pathway aberrations with response.

Citation Format: Moulder S, Hess K, Rauch M, Astrada B, Litton J, Mittendorf E, Ueno N, Tripathy D, Lim B, Piwnica-Worms H, Thompson A, Symmans WF. NCT02456857: A phase II trial of liposomal doxorubicin, bevacizumab and everolimus (DAE) in patients (pts) with localized triple-negative breast cancer (TNBC) with tumors predicted insensitive to standard neoadjuvant chemotherapy (NACT) [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr OT2-01-22.

Abstract P3-07-01: Selinexor, a selective inhibitor of nuclear export, demonstrates efficacy in preclinical models of triple negative breast cancer

Background: Approximately 15% of all breast cancers are categorized as triple negative (TNBC) for which the only chemotherapy is known to be effective, yet often fails to achieve remission. Nuclear exporter XPO1 (Exportin1 or CRM1) is a promising target for cancer therapy that mediates the transport of multiple tumor suppressors and cell cycle regulators that have been known to be relevant predictors in the mechanism and severity of TNBC. Given the pressing need for novel therapies for this disease, we sought to determine the antitumor effects of selinexor, a novel inhibitor of nuclear export, on triple negative breast cancers in vitro and in vivo as well as to address its mechanism of action.

Methods: 26 breast cancer cell lines of different breast cancer subtypes were treated with selinexor in vitro. Using cell proliferation assays the half maximal inhibitory concentration (IC50) was calculated using isobologram curves after 3 days of treatment; sensitivity was defined as IC50 &lt;1000nM. We then assessed mechanistic effects on apoptosis and cell proliferation using flow cytometry analysis with annexin V and propidium iodide and using western blot analysis we also studied its effects on markers of inhibition of apoptosis. In vivo efficacy was studied as single agent and in combination with standard chemotherapy agents in TNBC patient derived xenografts (PDXs) with varying levels of sensitivity to chemotherapy as well as with varying statuses of TP53 and PIK3CA, and gene expression subtypes.

Results: Selinexor demonstrated growth inhibition in all fourteen TNBC cell lines tested; TNBC cell lines were more sensitive to selinexor (median IC50 44nM, range 11 - 550nM), compared to ER+ cells lines (median IC50 of 13000 nM, range of 40nM - &gt; 1000 nM; P=0.017). Treatment with selinexor decreased expression levels of XPO1, as well as survivin and XIAP, and induced apoptosis. In multiple TNBC cell lines selinexor was synergistic with paclitaxel, carboplatin, eribulin and doxorubicin in vitro (median combination index 0.6, range 0.5-0.8). Selinexor as a single agent reduced tumor growth in vivo in 4 of 5 different TNBC PDX models with a median tumor growth inhibition ratio score (T/C) of 48% (range 34-59%) and demonstrated greater antitumor efficacy in combination with paclitaxel or eribulin with an average T/C score of 27% and 12% respectively.

Conclusions: Selinexor is a promising therapeutic agent for triple negative breast cancer and it has potential as a combination agent with standard chemotherapy.

Citation Format: Paez Arango N, Evans KW, Zhao M, Yuca E, Scott SM, Janku F, Ueno NT, Tripathy D, Kim C, Naing A, Funda M-B. Selinexor, a selective inhibitor of nuclear export, demonstrates efficacy in preclinical models of triple negative breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P3-07-01.

Abstract P1-05-01: Landscape of somatic mutations in inflammatory breast cancer whole-genome sequences

Goal: Inflammatory breast cancer (IBC) is a rare, aggressive form of breast cancer that is characterized by a highly metastatic phenotype. Numerous previous attempts failed to identify, recurrent, IBC-specific gene expression or DNA copy number alterations. We performed whole genome sequencing (WGS) of IBC biopsies obtained before any therapy to define a comprehensive genomic landscape of this disease.

Methods: Illumina paired-end whole genome sequencing (WGS) of 20 IBC (n=9 ER+, n=11 ER-) and matched normal samples were performed with median coverage of 60X and 40X for cancer and normal, the percentages of mapped reads were 99.3% and 99.2%, respectively. We identified germ-line and somatic variants, indels as well as large scale structural variants, using GATK Haplotype Caller, MuTect and CREST, respectively. We performed the same analysis on WGS data from 23, age, race and ER and HER2 matched, non-IBC (n=12 ER+, n=11 ER-) from the TCGA for comparison. Variants in both coding and noncoding sequences were categorized by FunSeq to identify potential drivers. Mutation clustering in each gene, as well as significantly mutated non-coding regulatory modules, were identified using LARVA. DeconstructSigs were used to decompose the mutational spectrum of each cancer into 30 validated, mutational signatures provided by COSMIC. Contributions of each validated signature to mutations in IBC vs. non-IBC were compared using Welch's t-test.

Results: We identified 118,818 somatic variants in the IBC samples (median: 3,856; minimum: 1,109; maximum: 24,815) including 1,060 variants (~0.9%) in coding regions. 5,287 somatic indels and 5,959 large scale structural variants were detected including 1,028 insertions and 1,857 deletions. Recurrent, non-synonymous mutations were detected in the coding region of GRIN2A gene in 3/20 IBC samples (15%), (previously reported as a potential driver mutation in 1.7% of breast cancers). Other significant mutations in coding regions included GRHL1, PIK3R2, ESR1, FLG2 and etc. Three DNase I hypersensitive sites (DHSs) in non-coding regions were altered in 20% (4/20) IBC samples vs. fewer than 8.7% (2/23) in non-IBC. Mutational frequency of GATA3 is 80.0% vs. 47.8% (p=0.03), and PTEN is 45.0% vs. 73.9% (p=0.05), in IBC vs. non-IBC samples when including both coding and non-coding variants. Contributions of mutational signature 9, that is associated with polymerase η , were significantly higher in IBC cohort than non-IBC cohort (p-value=0.056).

Conclusion: This is the first whole genome sequencing analysis of IBC and comparison with the results from non-IBC. We identified promising candidate drivers in the coding sequence and in non-coding regulatory modules of expressed genes. We also identified mutational signature 9, and mutations in several DHS as significantly more frequent alterations in IBC compared to non-IBC.

Citation Format: Li X, Krishnamurthy S, Kumar S, Reddy S, Woodward W, Reuben J, Hatzis C, Ueno NT, Gerstein M, Pusztai L. Landscape of somatic mutations in inflammatory breast cancer whole-genome sequences [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P1-05-01.

Abstract P3-05-04: Impact of androgen receptor expression in fluoxymesterone-treated, estrogen receptor–positive metastatic breast cancer exposed to contemporary hormonal therapy

Background: The use of the nonselective androgen fluoxymesterone in patients with metastatic breast cancer (MBC) diminished after the 1960s because of its adverse events and a limited understanding of its biological effects. Although fluoxymesterone has had efficacy against tamoxifen-resistant disease in clinical studies, its role in the era of contemporary hormonal therapy is unclear. Recent studies have shown that the androgen–androgen receptor (AR) complex acts as a suppressor of estrogen receptor (ER)+ breast cancer. We hypothesized that fluoxymesterone is effective against MBC that progresses despite contemporary hormonal therapy and that the drug has more clinical benefit in patients with ER+AR+ disease than in patients with ER+AR- disease. We evaluated the survival outcomes of patients with MBC who received fluoxymesterone after contemporary hormonal therapy failed and evaluated the association between ER/AR status and survival outcomes in these patients.

Methods and Materials: We included 103 patients treated with fluoxymesterone who had already received at least one prior hormonal or cytotoxic treatment for MBC between January 1, 2000, and December 31, 2014, at a single institution. A pathologist reviewed these patients' tumors' ER and AR expression levels by immunohistochemical staining. Progression-free survival (PFS) was defined from the start of fluoxymesterone treatment to the date of disease progression or last follow-up. We used Cox regression analysis to examine univariate and multivariate correlates of PFS.

Results: Patients received a median of 3 (range: 0-10) prior hormonal therapies (aromatase inhibitors, tamoxifen, and/or fulvestrant) before fluoxymesterone. Of the 103 patients, 33 (32%) discontinued fluoxymesterone because of physician decision or adverse events, which included toxicity in 14 patients, and 70 (68%) were eligible for tumor response assessment by Response Evaluation Criteria in Solid Tumors. Of these 70 patients, 2 (3%) had a complete response, 7 (10%) had a partial response, and 21 (30%) had stable disease for at least 6 months, yielding a clinical benefit rate of 43%. The median PFS was 3.9 months (95% confidence interval: 3.2–5.3 months). The multivariate analysis revealed no significant association between PFS and the type or number of prior treatments. Thirty-nine patients (38%) had archived tumor slides available for AR staining. All 39 patients had ER+ disease; 5 had ≤1%, 5 had &gt;1% but &lt;10%, 18 had ≥10%, and 11 had no AR nuclear expression. AR positivity defined by the presence of any AR+ cells, ≥1% AR+ cells, or ≥10% AR+ cells was not significantly associated with survival outcome.

Conclusions: Fluoxymesterone showed objective tumor response and prolonged control of ER+ MBC refractory to contemporary endocrine therapy. The number and type of prior treatments did not impact the drug's clinical benefit, and AR+ status did not influence the clinical outcome. Fluoxymesterone should be considered for patients whose ER+ MBC progresses despite contemporary hormonal therapy, regardless of their AR status.

Citation Format: Kono M, Fujii T, Lyons GR, Huo L, Bassett R, Gong Y, Karuturi MS, Tripathy D, Ueno NT. Impact of androgen receptor expression in fluoxymesterone-treated, estrogen receptor–positive metastatic breast cancer exposed to contemporary hormonal therapy [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P3-05-04.

Abstract OT3-02-05: NCI-2016-00367: A phase IIB study of neoadjuvant ZT regimen (enzalutamide therapy in combination with weekly paclitaxel) for androgen receptor (AR)-positive triple-negative breast cancer (TNBC)

BACKGROUND: Approximately 50% of TNBC expresses AR by immunohistochemical (IHC) staining. Luminal androgen receptor (LAR) subtype is heavily enriched in hormonally regulated genes, yet negative for ER by IHC. LAR is associated with low pCR rates and long survival. Preclinical data have shown that taxanes inhibit translocation of AR from the cytoplasm to the nucleus where AR is activated. Combining paclitaxel with enzalutamide may inhibit the AR pathway synergistically thereby increasing pCR rates. We hypothesized that patients with AR-positive TNBC who have chemo-insensitive disease (CID) after initial anthracycline-based chemotherapy treated with ZT would have higher RCB-0 and RCB-I rates than those who receive conventional taxane-based chemotherapy. Our team developed a clinical trial to identify patients with CID (ARTEMIS: A Randomized, TNBC Enrolling trial to confirm Molecular profiling Improves Survival). In the ARTEMIS trial, treatment-naïve patients with localized TNBC undergo a pretreatment biopsy and then begin anthracycline-based chemotherapy. Molecular testing results and radiographic response assessment are used to identify CID and will guide the second phase of neoadjuvant chemotherapy (NACT) to overcome CID.

PRIMARY OBJECTIVE: To determine RCB-0 and RCB-I rates of patients with TNBC who have CID to initial anthracycline-based chemotherapy and who received ZT.

TRIAL DESIGN AND STATISTICAL METHODS: Patients with CID from the ARTEMIS trial can enroll in the 12-week ZT (paclitaxel, 80 mg/m2 intravenously per week; enzalutamide, 160 mg orally per day). We will define pCR (RCB-0) or RCB-I as a response, using a Simon optimal 2-stage design with alpha=beta=10% and then setting the threshold for an acceptable pCR or RCB-I rate at 20%. We will enroll 12 patients into the first stage. If no patients experience pCR or RCB-I, we will stop the study after the first stage. If at least 1 patient experiences pCR or RCB-I, we will enroll 25 more patients for a total of 37 patients. We would declare the treatment worthy of further study if at least 4 of the 37 patients experience pCR or RCB-I. This design has a 54% probability of early termination after the first stage if the true pCR or RCB-I probability is 5%. Because patients with CID have a very low chance (5%) of achieving pCR with additional chemotherapy, improving pCR rates to 20% in this patient population would be clinically meaningful.

BRIEF ELIGIBILITY CRITERIA: Inclusion criteria: Primary invasive TNBC patients who have CID under the ARTEMIS trial; AR+ ≥1% nuclear staining by IHC; and adequate physical, organ, bone marrow, and cardiac functions. Exclusion criteria: Pregnant or lactating patients, history of colitis or absorption abnormality, known or suspected brain metastasis or leptomeningeal disease, or history of seizure.

CORRELATIVE SCIENCE: Enumeration of circulating tumor cells (CTCs) and expression of CTC-related gene transcripts will be measured to correlate CTC characteristics and/or gene profiles related to the AR pathway and treatment response to ZT.

Citation Format: Fujii T, Lim B, Helgason T, Hess KR, Gilcrease MZ, Willey JS, Tripathy D, Litton JK, Moulder S, Krishnamurthy S, Yang W, Reuben JM, Symmans WF, Ueno NT. NCI-2016-00367: A phase IIB study of neoadjuvant ZT regimen (enzalutamide therapy in combination with weekly paclitaxel) for androgen receptor (AR)-positive triple-negative breast cancer (TNBC) [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr OT3-02-05.