Short-Term Biomarker Modulation Study of Dasatinib for Estrogen Receptor-Negative Breast Cancer Chemoprevention

Objective

Risk-reducing therapy with selective estrogen receptor (ER) modulators and aromatase inhibitors reduce breast cancer risk. However, the effects are limited to ER-positive breast cancer. Therefore, new agents with improved toxicity profiles that reduce the risk in ER-negative breast cancers are urgently needed. The aim of this prospective, short-term, prevention study was to evaluate the effect of dasatinib, an inhibitor of the tyrosine kinase Src, on biomarkers in normal (but increased risk) breast tissue and serum of women at high risk for a second, contralateral primary breast cancer.

Materials and Methods

Women with a history of unilateral stage I, II, or III ER-negative breast cancer, having no active disease, and who completed all adjuvant therapies were eligible. Patients underwent baseline fine-needle aspiration (FNA) of the contralateral breast and serum collection for biomarker analysis and were randomized to receive either no treatment (control) or dasatinib at 40 or 80 mg/day for three months. After three months, serum collection and breast FNA were repeated. Planned biomarker analysis consisted of changes in cytology and Ki-67 on breast FNA, and changes in serum levels of insulin-like growth factor 1 (IGF-1), IGF-binding protein 1, and IGF-binding protein 3. The primary objective was to evaluate changes in Ki-67 and secondary objective included changes in cytology in breast tissue and IGF-related serum biomarkers. Toxicity was also evaluated.

Results

Twenty-three patients started their assigned treatments. Compliance during the study was high, with 86.9% (20/23) of patients completing their assigned doses. Dasatinib was well tolerated and no drug-related grade 3 and 4 adverse events were observed. Since only one patient met the adequacy criteria for the paired FNA sample, we could not evaluate Ki-67 level or cytological changes. No significant change in serum biomarkers was observed among the three groups.

Conclusion

Dasatinib was well tolerated but did not induce any significant changes in serum biomarkers. The study could not fulfill its primary objective due to an inadequate number of paired FNA samples. Further, larger studies are needed to evaluate the effectiveness of Src inhibitors in breast cancer prevention.

Feasibility and Safety of Personalized, Multi-Target, Adoptive Cell Therapy (IMA101): First-in-Human Clinical Trial in Patients with Advanced Metastatic Cancer

IMA101 is an actively personalized, multi-targeted adoptive cell therapy (ACT), whereby autologous T cells are directed against multiple novel defined peptide-HLA (pHLA) cancer targets. HLA-A*02:01-positive patients with relapsed/refractory solid tumors expressing ≥1 of 8 predefined targets underwent leukapheresis. Endogenous T cells specific for up to 4 targets were primed and expanded in vitro. Patients received lymphodepletion (fludarabine, cyclophosphamide), followed by T-cell infusion and low-dose IL2 (Cohort 1). Patients in Cohort 2 received atezolizumab for up to 1 year (NCT02876510). Overall, 214 patients were screened, 15 received lymphodepletion (13 women, 2 men; median age, 44 years), and 14 were treated with T-cell products. IMA101 treatment was feasible and well tolerated. The most common adverse events were cytokine release syndrome (Grade 1, n = 6; Grade 2, n = 4) and expected cytopenias. No patient died during the first 100 days after T-cell therapy. No neurotoxicity was observed. No objective responses were noted. Prolonged disease stabilization was noted in three patients lasting for 13.7, 12.9, and 7.3 months. High frequencies of target-specific T cells (up to 78.7% of CD8+ cells) were detected in the blood of treated patients, persisted for >1 year, and were detectable in posttreatment tumor tissue. Individual T-cell receptors (TCR) contained in T-cell products exhibited broad variation in TCR avidity, with the majority being low avidity. High-avidity TCRs were identified in some patients' products. This study demonstrates the feasibility and tolerability of an actively personalized ACT directed to multiple defined pHLA cancer targets. Results warrant further evaluation of multi-target ACT approaches using potent high-avidity TCRs. See related Spotlight by Uslu and June, p. 865.

Phase 1b study of combined selinexor and eribulin for the treatment of advanced solid tumors and triple-negative breast cancer

BACKGROUND

Selinexor (KPT-330) is a potent inhibitor of exportin 1 (XPO1), in turn inhibiting tumor growth. Selinexor enhances the antitumor efficacy of eribulin in triple-negative breast cancer (TNBC) in vitro and in vivo. Given the unmet medical need in TNBC and sarcoma, the authors explored the safety and efficacy of this combination.

METHODS

The authors conducted a phase 1b trial of combined selinexor and eribulin using a 3 + 3 dose-escalation design in patients who had advanced solid tumors and in those who had TNBC in a dose-expansion cohort.

RESULTS

Patients with TNBC (N = 19), sarcoma (N = 9), and other cancers (N = 3) were enrolled in the dose-escalation cohort (N = 10) and in the dose-expansion cohort (N = 21). The median number lines of prior therapy received was four (range, from one to seven prior lines). The most common treatment-related adverse events for selinexor were nausea (77%), leukopenia (77%), anemia (68%), neutropenia (68%), and fatigue (48%). One dose-limiting toxicity occurred at the first dose level with prolonged grade 3 neutropenia. The recommended phase 2 dose was 80 mg of selinexor orally once per week and 1 mg/m² eribulin on days 1 and 8 intravenously every 3 weeks. The objective response rate (ORR) was 10% in three patients. In the dose-escalation cohort, the ORR was 10%, whereas six patients with had stable disease. In the TNBC dose-expansion cohort (n = 18), ORR was 11%, and there were two confirmed partial responses with durations of 10.8 and 19.1 months (ongoing).

CONCLUSIONS

Selinexor and eribulin had an acceptable toxicity profile and modest overall efficacy with durable responses in select patients.

PLAIN LANGUAGE SUMMARY

Effective therapies for advanced, triple-negative breast cancer and sarcoma represent an unmet need. Exportin 1 is associated with the transport of cancer-related proteins. Preclinical studies have demonstrated tumor growth inhibition and enhanced tumor sensitivity in patients who receive selinexor combined with eribulin. In this phase 1b study, the authors evaluated the safety profile and clinical activity of the combination of selinexor, a potent oral inhibitor of exportin 1, and eribulin in patients with advanced cancers enriched for triple-negative breast cancer or sarcoma. The combination was well tolerated; most adverse events were mild or moderate, reversible, and managed with dose modifications or growth factor support. The combination of selinexor and eribulin produced an antitumor response, particularly in some patients with triple-negative breast cancer. This work lays the foundation for prospective investigations of the role of selinexor and eribulin in the treatment of triple-negative breast cancer.

Abstract P3-02-03: A phase Ib trial of bintrafusp alfa and eribulin in patients with metastatic triple negative breast cancer (TNBC)

Background: Metastatic TNBC is an aggressive breast cancer subtype with poor prognosis and limited systemic therapy options. While pembrolizumab in combination with chemotherapy is approved for PD-L1 positive TNBC, limited immunotherapy options exist for patients with progressive and/or PD-L1 negative disease. TGFβ released by cancer cells and stromal fibroblasts attenuates the intrinsic antitumor potential of immune cells within the tumor microenvironment mediating resistance to immunotherapy. Consequently, inhibition of TGFβ signaling could potentially enhance antitumor responses to anti-PD-L1/PD-1 therapies. Bintrafusp alfa is a bifunctional fusion protein composed of the extracellular domain of TGF-β receptor II (a TGF-β “trap”) fused to a human IgG1 monoclonal antibody blocking programmed cell death ligand 1. Preclinical studies have shown that eribulin downregulates TGFβ by phosphorylation of Smad proteins. Therefore, combining eribulin with bintrafusp alfa may have a synergistic effect. This study evaluated the combination of bintrafusp alfa with eribulin in patients with metastatic TNBC. Methods: This is a phase 1b, open label, single center study evaluating bintrafusp alfa in combination with eribulin in patients with metastatic TNBC who had relapsed/progressed on prior therapies. Patients with ER/PR ≤10% with measurable disease were enrolled. Patients who received prior anti-PD-1/PD-L1 therapies in the metastatic setting were excluded. Patients received bintrafusp alfa 1200 mg intravenously every 2 weeks in combination with eribulin (1.4 mg/m2 (dose level 1), 1.1 mg/m2, or 0.7 mg/m2) on days 1, 8, 22, 29 on every 6-week cycle. Primary objectives were to determine the recommended phase II dose (RP2D) as well as to evaluate the safety and tolerability of eribulin in combination with the fixed dose of bintrafusp alfa. Secondary objective was to determine the overall response rate (ORR) according to RECIST 1.1. Bayesian optimal interval (BOIN) design was employed to identify the RP2D. Toxicities assessed using CTCAE v4.03. Tumor assessments were performed every 6 weeks. Results: A total of 25 patients were enrolled on the study. Twenty-one patients were evaluable (3 screen failures, 1 received only one dose of study treatment). Median age 59 (range 27-85). Median number of prior therapies 2 (range 0-8). The most common reason for protocol discontinuation was disease progression (n = 15, 71%). Four patients experienced dose limiting toxicities (DLTs); 3 with decreased neutrophil count and 1 with increased aspartate aminotransferase. Five patients (24%) experienced grade 4 toxicities (increased aspartate aminotransferase, hypokalemia, hypophosphatemia, neutropenia). Nine patients (43%) experienced grade 3 toxicities. Three patients (14%) discontinued study due to toxicity. Total of 2 deaths were observed, none related to treatment. Most common toxicities (any grade) include anemia (n = 13 patients), elevated aspartate aminotransferase (11), neutropenia (n = 10), elevated aminotransferase (9), headache (n = 9), hypokalemia (n = 8), hyperglycemia (n = 8), leukopenia (n = 8), and fatigue (n = 8). RP2D was eribulin 1.1 mg/m2 with bintrafusp alfa 1200 mg. Six patients had PR (28.6%), 2 had SD (9.5%) and 12 had PD (57.1%) as the best response. One patient withdrew before response evaluation. Median PFS was 1.7 months (95% CI: (1.2, 5.9) and median OS was 11.1 months (95%CI: (5.2, 15.7). Conclusions: The combination of bintrafusp alfa with eribulin has manageable safety profile with meaningful clinical activity in patients with TNBC. Further studies evaluating TGF inhibitors in breast cancer are warranted.

Citation Format: Senthil Damodaran, Diane Liu, Jill Schwartz, Vicente Valero, David Ramirez, Sadia Saleem, Naoto T. Ueno, Nuhad K. Ibrahim, Meghan S. Karuturi, Rashmi K. Murthy, Stacy Moulder, Jennifer K. Litton. A phase Ib trial of bintrafusp alfa and eribulin in patients with metastatic triple negative breast cancer (TNBC) [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-02-03.

Abstract P4-06-09: A phase 1b study of neratinib with THP in metastatic and locally advanced breast cancer, and phase II study of THP followed by AC in HER2 + primary inflammatory breast cancer (IBC), and neratinib with taxol followed by AC in HR+/HER2- IBC

Background: The pathologic complete response (pCR) rate in inflammatory breast cancer (IBC) patients is worse than in non-IBC patients; new drug combinations are warranted to improve pCR rates across all IBC molecular subtypes. Based on our preclinical data, we added neratinib to standard neoadjuvant chemotherapy in both HER2+ (synergy) and HER2-/hormone receptor (HR)+ (high frequency of ERBB2 mut) untreated IBC, as a single-center, non-randomized phase I/II trial. Patients and Method: This study enrolled three cohorts: Cohort I phase Ib (C1P1B), Cohort I Phase II (C1P2) and Cohort II (C2). In C1P1B to determine the recommended phase 2 dose (RP2D), we enrolled patients with HER2+ metastatic or locally advanced breast cancer. Patients received paclitaxel/trastuzumab/pertuzumab (THP) + neratinib x 4 cycles (up to 8 cycles per physician’s discretion). For C1P2 and C2, we enrolled Stage III – IV primary IBC patients. In C1P2, patients with HER2+ IBC received neratinib (RP2D) combined with THP x 4 cycles followed by doxorubicin/cyclophosphamide (AC) x 4 cycles. Per stage I design, 11 patients were enrolled with plan to enroll 20 more patients in Stage II if at least 6 had a pCR. In C2, patients with HER2-/HR+ IBC received neratinib 200 mg/day combined with paclitaxel x 4 cycles followed by AC x 4 cycles. Stage I design planned for enrollment of 16 patients with enrollment of 15 more patients on stage II, if at least 2 Stage I patients had pCR. In all three cohorts, patients initiated prophylactic anti-diarrheal medication (loperamide & budesonide) with the first dose of neratinib. Results: From 2018 to 2022, thirty-four patients were enrolled and treated (n=4 C1P1B, n=14 C1P2, n=16 C2). In C1P1B, observed DLTs (dose limiting toxicities) were Grade (Gr) 2 Diarrhea, n=2 (50%); Gr3 diarrhea, n=2 (50%); 2 patients had a serious adverse event (SAE); 3 patients (55%) had Gr2 nausea. The RP2D was established at 80 mg/day (dose level 0). For patients in C1P2, the most frequently occurring adverse events (AEs) included Gr2 Alopecia, n=14 (100%); Gr2&3 Diarrhea, n=14 (100%); Gr2/3 Nausea, n=12 (86%); Gr2/3 Anemia, n=7 (50%); Gr2/3 Fatigue, n=8 (57%); Gr2/3 Hypokalemia, n=6 (57%); and Gr2/3 Neutrophil count decreased, n= 7 (50%). 6 patients had an SAE. Of the first 11 patients, 5 (46%) had pCR, 1 (9%) RCB-1, 1 (9%) RCB-II and 1 (9%) RCB-III. Three patients stopped study treatment for toxicity (27%), were non-evaluable and replaced. Of these, one had RCB-III (33.3%), one progression of disease (PD) (33.3%), and one came off study for toxicity (33.3%). Rather than replacing additional non-evaluable patients, the study was closed to new patient accrual. In C2, the most frequently occurring AEs were Gr2 diarrhea, n=7(44%); Gr3 diarrhea, n=8 (50%); Gr2 alopecia, n=14 (88%); Gr2/3 Anemia, n=10 (63%); Gr2/3 Nausea, n=7 (44%); Gr2/3 Neutropenia, n= 7 (44%). 3 patients had an SAE. Of 16 patients in this cohort, 1 had pCR (6%), 5 RCB-II (31%), 4 RCB-III (25%), 3 came off study for toxicity (19%) and 3 had PD (19%). C2 also closed to new patient accrual given the high toxicity profile. Conclusion: The addition of neratinib did not improve the pCR rate in HER2+ or HER2-/HR+ subtypes of IBC, and increased toxicities were observed. The trial closed to new patient entry March 2022. However, some patients achieved significant response. Biomarker analysis is ongoing. Evaluable participants will continue long-term follow-up per protocol. Acknowledgments: This study is supported by PUMA Biotechnology.

Citation Format: Angela N. Marx, Megumi Kai, Min Fu, Hope E. Murphy, Jie S. Willey, Huiming Sun, Angela Alexander, Roland L. Bassett, Gary J. Whitman, H. T. Carisa Le-Petross, Miral Patel, Banu K. Arun, Sausan Abouharb, Parijatham S. Thomas, Carlos H. Barcenas, Nuhad K. Ibrahim, Vicente Valero, Naoto T. Ueno, Rachel M. Layman, Bora Lim, Wendy Woodward, Anthony Lucci. A phase 1b study of neratinib with THP in metastatic and locally advanced breast cancer, and phase II study of THP followed by AC in HER2 + primary inflammatory breast cancer (IBC), and neratinib with taxol followed by AC in HR+/HER2- IBC [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-06-09.

Abstract HER2-01: HER2-01 Clinical and Molecular Characteristics of HER2-low/zero Early Stage Triple-Negative Breast Cancer

Background: In the metastatic setting, low HER2 expression is associated with clinical benefit from trastuzumab deruxtecan, a HER2-targeting antibody drug conjugates. However, little is known about the biological significance of low HER2 expression in patients with early stage triple-negative breast cancer (TNBC) receiving neoadjuvant therapy (NAT). Methods: Out of 595 patients with stage I-III TNBC enrolled on the prospective ARTEMIS trial (NCT02276443) from 2015-2021, we identified 367 patients with available HER2 immunohistochemistry (IHC) results on pre-NAT tumor tissue (HER2-zero: n=218; HER2-low [IHC 1+, 2+]: n=149). All patients were treated with anthracycline-based NAT. In cases where sufficient pre-NAT tumor tissue were available, additional IHC and/or RNAseq were performed. Differential gene expression (DGE) and pathway analysis were performed using DEseq2. Gene set enrichment analysis (GSEA) was performed using the Hallmark gene sets. Deconvolution analyses were performed using CIBERSORT. We controlled for multiple hypothesis using a false discovery rate (FDR) threshold with the Benjamini-Hochberg method, accepting as significant genes with at least a 2-fold change and < 5% FDR. Results: Table 1 summarizes baseline clinicopathological features of the 367 patients. Compared to HER2-zero tumors, HER2-low tumors were less likely of metaplastic histology (p=0.001), associated with lower Ki67 (p=0.017) and were more likely to be androgen receptor (AR)-positive (p=0.01). There were no significant differences in tumor-infiltrating lymphocytes (TILs) infiltration and PD-L1 expression between HER2-zero and HER2-low tumors. Among the 226 patients with sufficient pre-NAT tissue for RNAseq, DGE analyses demonstrated upregulation of genes involved in fatty acid metabolism (ACSM1) and steroid hormone metabolism (DHRS2, UGT2B28) in HER2-low tumors compared with HER2-zero tumors. Deconvolution analyses revealed no significant differences between predicted proportions of immune cell subpopulations between HER2-low and HER2-zero tumors. Although rates of pCR were not significantly different between patients with HER2-zero (46%) and HER2-low tumors (40%) (p=0.34), non-pCR in patients with HER2-low tumors was associated with increased expression of EREG, which encodes an EGFR ligand, while non-pCR in patients with HER2-zero tumors was associated with downregulation in genes involved in immune response pathways. GSEA further identified the Hallmark allograft rejection (FDR q=0.001), interferon gamma response (FDR q=0.002), and interferon alpha response pathways (FDR q=0.007) as the 3 most significantly downregulated pathways in HER2-zero tumors from patients experiencing a non-pCR relative to HER2-zero tumors from patients experiencing a pCR. Conclusion: In early stage TNBC, low HER2 expression is associated with increased AR expression and upregulation of genes associated with fatty acid and steroid hormone metabolism. Gene expression analyses suggest that drivers of resistance to NAT differ between HER2-low and HER2-zero tumors. Biological differences between HER2-zero and HER2-low tumors exist and may influence future personalized treatment for patients with early stage TNBC.

Citation Format: Clinton Yam, Ziyi Li, Anil Korkut, Wencai Ma, Elisabeth Kong, Holly A. Hill, Hussein Abbas, Sausan Abouharb, Beatriz Adrada, Banu K. Arun, Carlos H. Barcenas, Ajit Bisen, Daniel Booser, Aman Buzdar, Rosalind Candelaria, Junjie Chen, Alyson Clayborn, Senthil Damodaran, Qingqing Ding, Haven Garber, Gabriel N. Hortobagyi, Kelly K. Hunt, Nuhad K. Ibrahim, Adaeze Iheme, Meghan S. Karuturi, Kimberly Koenig, Rachel M. Layman, Jangsoon Lee, Jennifer K. Litton, Melissa Mitchell, Giancarlo Moscol, Jason Mouabbi, Rashmi K. Murthy, Oluchi Oke, Paula Pohlmann, David Ramirez, Elizabeth Ravenberg, Sadia Saleem, Mediget Teshome, Vicente Valero, Jason White, Madison Williams, Wendy Woodward, Chasity Yajima, Naoto T. Ueno, Ken Chen, Gaiane Rauch, Lei Huo, Debu Tripathy. HER2-01 Clinical and Molecular Characteristics of HER2-low/zero Early Stage Triple-Negative Breast Cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr HER2-01.

Phase Ib study of selinexor and eribulin combination in advanced solid tumors and triple-negative breast cancer

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Background: Selinexor (KPT-330) is potent inhibitor of Exportin-1. In vitro, Selinexor was found to be synergistic with eribulin in triple negative breast cancer (TNBC) cell lines and enhanced antitumor activity of eribulin in TNBC patient-derived xenografts (PMID 28810913). Methods: We conducted a phase Ib trial in combination of selinexor and eribulin using 3 + 3 design in dose escalation for patients with advanced solid tumors and in TNBC in dose expansion cohort. Eribulin could be discontinued after combination for 6 cycles at physician discretion. Primary objectives: Safety, Recommended Phase 2 Dose (RP2D). Secondary Objectives: Objective Response Rate (ORR), Duration of Response (DOR), Disease Control Rate (DCR), Overall Survival (OS) and Progression Free Survival (PFS). Results: 31 patients, TNBC (n = 19), sarcoma (n = 8), others (n = 4) enrolled in dose escalation (n = 10) and dose expansion phases (n = 21). Median prior therapies:4 (1–6). Study initiated selinexor at 60mg twice weekly and eribulin 1.4mg/m2 on Day1, Day8 every 3 weeks which led to 1 Dose Limiting Toxicity (DLT) and hence, selinexor 80mg once weekly and eribulin 1mg/m2 was elected as RP2D due to efficacy and tolerability. As of 01/15/2022, of 29 patients (94%) who have discontinued treatment, 24 (77%) were due to progressive disease, 3 (10%) withdrew consent and 2 (6%) due to toxicities (G1 pneumonitis; G3 neutropenia) while 2 (6%) remain on trial. All 31 patients had at least one treatment emergent adverse event (TEAE) while most prevalent TEAEs (all grades) were leukopenia (77%), nausea (71%), anemia and neutropenia (68%) and fatigue (48%). The most common G3/4 TEAE were leukopenia (26%) and neutropenia (29%). 2 DLTs occurred; 1 in first dose level (DL); 1 in second DL dosed at selinexor 80 mg once weekly due to G3 neutropenia. ORR for all was 10% while DCR (SD+PR+CR) > 6 months seen in 3 (15%) TNBC and 2 (20%) sarcoma patients. The median OS and PFS for all were 12.3 (7.3, 27.3) months and 2.3 (1.6, 4.1) months. In dose escalation cohort, ORR was 10% where one patient (3%) with vaginal SCC had confirmed PR (-44%) for 2.1 months. Five patients (62.5%) with sarcoma had stable disease (SD). One patient with high grade sarcoma has SD for 68 months and remains on selinexor after 4 months of eribulin and selinexor. In TNBC dose expansion (n = 19), ORR was 10.5% with 2 confirmed PRs and median duration of response (DOR) of 10.8 months. One patient who has remained on treatment for 18 months, and after receiving 8 months of eribulin and selinexor, remains on selinexor with 100% target regression and an indeterminate brain lesion. Conclusions: Selinexor with eribulin is safe with manageable toxicity profile and modest overall clinical efficacy. Durable responses and disease control were observed with metastatic TNBC. Further study is needed to examine the determinants of response to this combination. Clinical trial information: NCT02419495.

Incidence and impact of brain metastasis in patients with hereditary BRCA1 or BRCA2 mutated invasive breast cancer

Patients with hereditary mutations in BRCA1 or BRCA2 (gBRCA1/2) and breast cancer have distinct tumor biology, and encompass a predilection for brain metastasis (BM). We looked into baseline risk of BMs among gBRCA1/2 patients. Patients with gBRCA1/2, stage I-III invasive breast cancer seen between 2000–2017 with parenchymal BMs. Among gBRCA1 with distant breast cancer recurrence, 34 of 76 (44.7%) were diagnosed with brain metastases compared to 7 of 42 (16.7%) patients with gBRCA2. In the comparator group, 65 of 182 (35.7%) noncarrier triple-negative breast cancer (TNBC) and a distant recurrence experienced BM’s. In a competitive risk analysis using death as a competing factor, the cumulative incidence of BMs was similar between gBRCA1 and noncarrier TNBC patients. The time from primary breast cancer diagnosis to detection of BMs was similar between gBRCA1 and noncarrier TNBC patients (2.4 vs 2.2 years). Survival was poor after BMs (7.8 months for gBRCA1 patients vs. 6.2 months for TNBC noncarriers). Brain was a more common site of initial distant recurrence in gBRCA1 patients versus TNBC noncarriers (26.3% vs. 12.1%). Importantly, the presence of BMs, adversely impacted overall survival across groups (HR 1.68 (95% CI 1.12–2.53), hazard ratio for death if a patient had BMs at the time of initial breast cancer recurrence vs. not). In conclusion, breast cancer BMs is common and is similarly frequent among gBRCA1 and noncarrier patients with recurrent TNBC. Our study highlights the importance of improving the prevention and treatment of BMs in patients with TNBC, gBRCA1 carriers, and noncarriers.

RADI-17. Outcomes for patients with triple negative breast cancer treated with upfront stereotactic radiosurgery for brain metastases

Background

Triple-negative breast cancer (TNBC) is an aggressive subtype with high propensity of developing brain metastases (BM). Clinical outcomes and prognostic factors after stereotactic radiosurgery (SRS) for BM were not well defined.

Methods

We identified 57 consecutive TNBC patients (pts) treated with single fraction SRS for BM during 05/2008–04/2018. Overall survival (OS) from BM diagnosis and freedom from BM progression (FFBMP) after initial SRS were evaluated. BM progression was defined as local and/or distant brain failure (LBF, DBF) after SRS. Kaplan-Meier analyses and Cox proportional hazard regression were used to estimate survival outcomes and identify prognostic factors.

Results

The median time to BM development from TNBC diagnosis was 23.7 months (mo) (range 0.7‒271.1). Median OS was 13.1 mo (95%CI 8.0‒19.5). On univariate analysis, Karnofsky performance score (KPS) >70 (p=0.03), number of BMs <3 (p=0.016), and BM among the first metastatic sites (p=0.04) were associated with longer OS. On multivariate analysis, KPS ≤70 was associated with higher risk of death (HR 3.0, p=0.03). Of 46 pts with adequate imaging follow-up, 29 (63%) had intracranial progression with a median FFBMP of 7.4 mo (95% CI 5.7–12.7). At 12 mo the estimated cumulative DBF rate was 61.1% (95%CI 40.8%–74.4%) and LBF rate was 17.8% (95%CI 2%–31.1%). Number of BMs (≥3 vs <3) was not associated with FFBMP (p=0.7). Of the 29 pts with BM progression, additional radiation therapy (RT) (vs. no RT) was associated with improved survival (21.7 vs. 7.0 mo, p<0.0001).

Conclusions

TNBC pts with BM treated with SRS had an OS of 13.1 mo and FFBMP of 7.4 mo. Good KPS was an independent prognostic factor for OS. Further studies with more pts or conducted prospectively are needed to better understand and to improve treatment outcomes in this pt population.

Molecular Spectra and Frequency Patterns of Somatic Mutations in Arab Women with Breast Cancer

BACKGROUND

The role of somatic mutations in breast cancer prognosis and management continues to be recognized. However, data on the molecular profiles of Arab women are limited.

MATERIALS AND METHODS

This was a cross-sectional study based on medical chart review of all Arab women diagnosed with breast cancer at a single institution between 2010 and 2018 who underwent next-generation sequencing with Ampliseq 46-Gene or 50-Gene.

RESULTS

A total of 78 Arab women were identified, with a median age at diagnosis of 52.3 years (range: 37-82 years; 38.5% ≤50 years). The majority of patients had stage III or IV disease (74.4%). Next-generation sequencing revealed the following somatic mutation rates: TP53, 23.1%; ATM, 2.6%; IDH1, 2.6%; IDH2, 3.8%; PTEN, 7.7%; PIK3CA, 15.4%; APC, 7.7%; NPM1, 2.5%; MPL, 1.3%; JAK2, 2.5%; KIT, 7.7%; KRAS, 3.8%; and NRAS, 3.8%.

CONCLUSION

Our study illustrates frequencies of somatic mutations in Arab women with breast cancer and suggests potential variations from estimates reported in the Western population. These data calls for larger epidemiologic studies considering the evolving role of such mutations in prognostication and personalized management.

Ixabepilone: Overview of Effectiveness, Safety, and Tolerability in Metastatic Breast Cancer

Treatment algorithms for metastatic breast cancer describe sequential treatment with chemotherapy and, if appropriate, targeted therapy for as long as the patient receives benefit. The epothilone ixabepilone is a microtubule stabilizer approved as a monotherapy and in combination with capecitabine for the treatment of metastatic breast cancer in patients with demonstrated resistance to anthracyclines and taxanes. While chemotherapy and endocrine therapy form the backbone of treatment for metastatic breast cancer, the epothilone drug class has distinguished itself for efficacy and safety among patients with disease progression during treatment with chemotherapy. In phase III trials, ixabepilone has extended progression-free survival and increased overall response rates, with a manageable toxicity profile. Recent analyses of subpopulations within large pooled datasets have characterized the clinical benefit for progression-free survival and overall survival for ixabepilone in special populations, such as patients with triple-negative breast cancer or those who relapsed within 12 months of prior treatment. Additional investigation settings for ixabepilone therapy discussed here include adjuvant therapy, weekly dosing schedules, and ixabepilone in new combinations of treatment. As with other microtubule stabilizers, ixabepilone treatment can lead to peripheral neuropathy, but evidence-based management strategies may reverse these symptoms. Dose reductions did not appear to have an impact on the efficacy of ixabepilone plus capecitabine. Incorporation of ixabepilone into individualized treatment plans can extend progression-free survival in a patient population that continues to represent an unmet need.

Upfront stereotactic radiosurgery for brain metastases from triple-negative breast cancer

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Background: Triple-negative breast cancer (TNBC) is an aggressive subtype with high propensity of brain metastases (BM). Outcomes after upfront stereotactic radiosurgery (SRS) for BM from TNBC patients are not well defined. We evaluated outcomes and identified prognostic factors for such patients. Methods: We reviewed 57 consecutive patients treated with upfront SRS for BM from TNBC in May 2008–April 2018 at a large-volume cancer center. Endpoints were overall survival (OS) from BM diagnosis and freedom from BM progression (FFBMP) after initial SRS. BM progression was defined as local and/or distant brain failure (LBF or DBF) after initial SRS; LBF was radiographic progression of treated lesions, assessed by a neuroradiologist or treating physician excluding post-radiation changes or radiation necrosis. Kaplan-Meier and Cox proportional hazard regression analyses were used to estimate survival outcomes and identify prognostic factors. Results: In this cohort of 57 patients with a median age of 53 y (range 26–82) at BM diagnosis and follow-up time of 12.2 months (mo, range 0.8–97.5), median time to BM development from TNBC diagnosis was 23.7 mo (range 0.7‒271.1). Estimated median OS time from initial BM diagnosis was 13.1 mo (95% CI 8.0‒19.5). In univariate analysis, Karnofsky performance score (KPS) > 70 (p = 0.03), having < 3 BMs (p = 0.016) at BM diagnosis, and BM as first site of metastasis (p = 0.041) were associated with longer OS. On multivariate analysis, KPS ≤70 was associated with higher risk of death (HR 3.0, p = 0.03). Of 46 patients with imaging follow-up for FFBMP assessment, 29 (63%) developed BM progression after initial SRS with an estimated median FFBMP of 7.4 mo (95% CI 5.7–12.7). Median times to LBF and DBF were 10 mo (range 0.3–97) and 5.9 mo (range 0.3–90.8). Estimated cumulative LBF rate was 17.8% (95% CI 2%–31.1%) and DBF 61.1% (95% CI 40.8%–74.4%) at 12 mo. Number of BMs at BM diagnosis (≥3 vs < 3) was not associated with FFBMP (p = 0.7). Of the 29 patients with BM progression, 5 did not receive salvage radiation therapy (RT) and 24 received salvage RT (SRS, whole-brain radiation [WBRT], or both SRS+WBRT). Receipt of salvage RT was associated with longer survival (median 21.7 mo vs. 7.0 mo for no salvage RT, p < 0.0001) and did not differ by type of salvage RT (median OS 18.6 mo for WBRT; 26.2 mo for SRS+WBRT; 35.9 mo for SRS, p = 0.08). Conclusions: We reported a median OS of 13.1 mo and FFBMP of 7.4 mo in TNBC patients with good local control. Good KPS was independent prognostic factor for better OS. FFBMP did not differ by number of SRS-treated brain lesions ( < 3 vs ≥3). Further prospective studies of larger numbers of patients needed for more accurate comparisons of treatment types.

The impact of gut microbial composition on response to neoadjuvant chemotherapy (NACT) in early-stage triple negative breast cancer (TNBC)

590

Background: The impact of gut microbiome on tumor biology, progression and response to immunotherapy has been shown across cancer types. However, there is little known about the impact of gut microbial composition on response to chemotherapy. We have previously shown that the gut microbiome remains unaltered during NACT in a cohort of 32 patients. Here we investigate the association between gut microbiome and response to NACT in a larger cohort of early-stage TNBC. Methods: Longitudinal fecal samples were collected from 85 patients with newly-diagnosed, early-stage TNBC patients enrolled in the ARTEMIS trial (NCT02276443). Patients all received standard NACT with adriamycin/cyclophosphamide (AC); volumetric change was assessed using ultrasound and patients with < 70% volumetric reduction (VR) after 4 cycles of AC were recommended to receive targeted therapy in addition to standard NACT to improve response rates. We performed 16S sequencing on bacterial genomic DNA extracted from 85 pre-AC fecal samples using the 2x250 bp paired-end read protocol. Quality-filtered sequences were clustered into Operational Taxonomic Units and classified using Mothur method with the Silva database version 138. For differential taxa-based univariate analysis, abundant microbiome taxa at species, genus, family, class, and order levels were analyzed using DESeq2 after logit transformation. Alpha-diversity indices within group categories were calculated using phyloseq. Microbial alpha diversity (within-sample diversity) was measured by Simpson's reciprocal index. β-diversity was measured using weighted UniFrac distances between the groups. The association between microbiota abundance and pathologic complete response (pCR) or residual disease (RD) was assessed using DESeq2 analysis. Results: Pre-AC fecal samples from 85 patients were available for analysis. Amongst them, there were 46 patients with pCR and 39 patients with RD. There was no significant difference in alpha diversity (p = 0.8) or beta-diversity (p = 0.7) between the pCR and RD groups. However, relative to patients with RD, the gut microbiome in patients with pCR was enriched for the Bifidobacterium longum species (p = 0.03). The gut microbiome in patients with RD was enriched for Lachnospiraceae (p = 0.03) at the genus level and the Bacteroides thetaiotaomicron species (p = 0.02). Conclusions: We have demonstrated significant differences in the gut microbial composition in patients with pCR as compared to patients with RD. Further investigation in larger studies is needed to support therapeutic exploration of gut microbiome modulation in TNBC patients receiving chemotherapy such as probiotic supplementation or fecal microbiota transplant.

Stereotactic radiosurgery (SRS) for brain metastasis (BM) in hormone receptor positive (HR+) HER2 negative breast cancer (BC)

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Background: With the increase of the utilization of SRS for the treatment of oligometastatic BM over surgical reaction or whole brain radiation therapy (WBRT), we sought to evaluate the impact of SRS on overall survival in HR+Her2- BC and prognostic factors associated with SRS. Methods: We reviewed prospectively collected data in the electronic data bases of the breast medical, surgical and radiation oncology departments at MD Anderson cancer center. We aimed at identifying HR+HER2- BC patients who received upfront SRS for BM’s between 08/10/2009 and 02/27/2018.Overall survival was defined as the time from the first SRS to last follow-up/death. Multivariate analysis by the Cox proportional hazards regression analysis was performed to evaluate the prognostic factors (age at BM, stage, Karnofsky performance score (KPS), symptomatic BM, BM at 1stdistant metastatic presentation, extracranial Disease, treatment history, salvage therapy, number of brain lesion treated) of SRS that influenced survival. Results: A total of 125 patients were identified, and we are reporting on 68 with completed analysis. Median age at time of first SRS was 53.86 years. 51 patients of the 68 were deceased at the time of this analysis and 17 patients were alive at the time of last follow-up. 49 patients (72.06 %) presented with radiation necrosis after SRS; 36 patients (52.94 %) presented with BM as 1st distant metastasis including metastasis to other sites. Number of BM’s lesions <4 was 60 (88.2%) and >=4 was 7 (10.3%). The median follow-up from time of first SRS for survivors was 10.84 months. 24 (35.29%) received two or more sessions of SRS and the mean time between first and second SRS sessions for these patients was 14.24 months. Median time from first SRS to second SRS for ER+HER2− patients was 10.84 months (n = 24); on multivariable analysis, higher Karnofsky performance score (KPS) was associated with better survival compared to no salvage therapy. Patients with KPS>90 (p=0.005) had better survival and reduced the hazard by a factor of 0.33 (or 67%). Receiving SRS (p=0.0003) or SRS+WBRT (0.0001) as salvage therapy reduced the hazard (risk of death) by 86% and 85%, respectively. Conclusions: SRS is an effective treatment modality for HR+HER2- BM from BC. Patients who received SRS or SRS and WBRT, KPS >90 had better survival than patients who didn’t receive any salvage therapy. Updated data will be available at the time of the presentation.[Table: see text]

Influencers of the Decision to Undergo Contralateral Prophylactic Mastectomy among Women with Unilateral Breast Cancer

Simple Summary

In this survey study, we examined survey responses from 397 women with stage 0 to III unilateral breast cancer and found that partners, physicians, and the media were significant relative to the patient’s own influence in their decision to undergo a CPM. The findings of this study may inform policy by highlighting the need for educational aids, programs, or tools that help women with unilateral breast cancer make informed, evidence-based decisions regarding CPM efficacy.

Abstract

(1) Background: The relatively high rate of contralateral prophylactic mastectomy (CPM) among women with early stage unilateral breast cancer (BC) has raised concerns. We sought to assess the influence of partners, physicians, and the media on the decision of women with unilateral BC to undergo CPM and identify clinicopathological variables associated with the decision to undergo CPM. (2) Patients and Methods: Women with stage 0 to III unilateral BC who underwent CPM between January 2010 and December 2017. Patients were surveyed regarding factors influencing their self-determined decision to undergo CPM. Partner, physician, and media influence factors were modeled by logistic regressions with adjustments for a family history of breast cancer and pathological stage. (3) Results: 397 (29.6%) patients completed the survey and were included in the study. Partners, physicians, and the media significantly influenced patients’ decision to undergo CPM. The logistic regression models showed that, compared to self-determination alone, overall influence on the CPM decision was significantly higher for physicians (p = 0.0006) and significantly lower for partners and the media (p < 0.0001 for both). Fifty-nine percent of patients’ decisions were influenced by physicians, 28% were influenced by partners, and only 17% were influenced by the media. The model also showed that patients with a family history of BC had significantly higher odds of being influenced by a partner than did those without a family history of BC (p = 0.015). (4) Conclusions: Compared to self-determination, physicians had a greater influence and partners and the media had a lower influence on the decision of women with unilateral BC to undergo CPM. Strong family history was significantly associated with a patient’s decision to undergo CPM.

Outcomes of changing systemic therapy in patients with relapsed breast cancer and 1 to 3 brain metastases

The development of brain metastases (BMs) in breast cancer (BC) patients remains a challenging complication. Current clinical practice guidelines recommend local treatment of BMs without changing systemic therapy (CST) in patients with stable extracranial disease. We retrospectively investigated the impact of CST (when applicable as per treating physician's discretion) following the diagnosis and management of oligometastatic (1-3) BMs in patients without extracranial metastases on the progression-free survival time (PFS), and overall survival (OS). Hazard ratios (HRs) were calculated using the Cox proportional hazard model. Among the 2645 patients with BC and BMs treated between 2002 and 2015, 74 were included for analysis. 40.5% of patients had HER2 + disease. Median time from diagnosis of BC to BMs was 17.6 months. 54%, 8%, and 38% of BMs were managed by radiation, craniotomy, or combination, respectively. Following the primary management of BMs, we observed that CST occurred in 26 (35.5%) patients, consisting of initiation of therapy in 13.5% and switching of ongoing adjuvant therapy in 22%. Median PFS was 6.6 months among patients who had CST compared to 7.1 months in those who did not (HR = 0.88 [0.52-1.47], p = 0.62). Median OS was 20.1 months among patients who had CST compared to 15.1 months in those who did not (HR = 0.68 [0.40-1.16], p = 0.16). Upon the successful local management of oligometastatic BMs in patients without extracranial disease, we did not find a significant difference in survival between patients who experienced a change in systemic therapy as compared to those who did not.

Phase I Study of Everolimus, Letrozole, and Trastuzumab in Patients with Hormone Receptor-positive Metastatic Breast Cancer or Other Solid Tumors

PURPOSE

Doublets of everolimus with letrozole or trastuzumab have demonstrated activity against HER2-positive breast cancer, suggesting that the triple combination can have synergistic anticancer activity.

PATIENTS AND METHODS

This first-in-human dose-escalation study (NCT02152943) enrolled patients with hormone receptor- positive, HER2-positive (defined by amplification, overexpression, or mutation) treatment-refractory advanced cancers to receive escalating doses (3+3 design) of daily oral letrozole (days 1-21), daily oral everolimus (days 1-21), and intravenous trastuzumab (day 1) every 21 days to determine dose-limiting toxicities (DLT) and MTD or recommended phase II dose (RP2D).

RESULTS

A total of 32 patients with hormone receptor-positive, HER2-positive (amplification, n = 27; overexpression, n = 1; and mutation, n = 4) advanced breast cancer (n = 26) or other cancers (n = 6) were enrolled. The most frequent grade ≥3 adverse events included hyperglycemia (n = 4), anemia (n = 3), thrombocytopenia (n = 2), and mucositis (n = 2). DLTs included grade 3 mucositis and grade 4 neutropenia, and trastuzumab given as an 8 mg/kg loading dose on day 1 of cycle 1 followed by a 6 mg/kg maintenance dose on day 1 of subsequent cycles plus 10 mg everolimus daily and 2.5 mg letrozole daily every 21 days was declared as RP2D. Five patients with breast cancer (four with HER2 amplification and one with HER2 mutation) had partial responses. HER2 amplification in circulating cell-free DNA at baseline was associated with shorter progression-free and overall survival durations (P < 0.05).

CONCLUSIONS

Everolimus, letrozole, and trastuzumab have a favorable safety profile and elicit encouraging signals of anticancer activity in patients with heavily pretreated hormone receptor- and HER2-positive advanced cancers.

Effects of systemic therapy and local therapy on outcomes of 873 breast cancer patients with metastatic breast cancer to brain: MD Anderson Cancer Center experience

Outcomes of treatments for patients with breast cancer brain metastasis (BCBM) remain suboptimal, especially for systemic therapy. To evaluate the effectiveness of systemic and local therapy (surgery [S], stereotactic radiosurgery [SRS] and whole brain radiotherapy [WBRT]) in BCBM patients, we analyzed the data of 873 BCBM patients from 1999 to 2012. The median overall survival (OS) and time to progression in the brain (TTP-b) after diagnosis of brain metastases (BM) were 9.1 and 7.1 months, respectively. WBRT prolonged OS in patients with multiple BM (hazard ratio [HR], 0.68; 95% CI, 0.52-0.88; P = .004). SRS alone, and surgery or SRS followed by WBRT (S/SRS + WBRT), were equivalent in OS and TTP-b (median OS, 14.9 vs 17.2 months; median TTP-b, 8.2 vs 8.6 months). Continued chemotherapy prolonged OS (HR, 0.35; 95% CI, 0.30-0.41; P < .001) and TTP-b (HR, 0.48; 95% CI, 0.33-0.70; P < .001), however, with no advantage of capecitabine over other chemotherapy agents used (median OS, 11.8 vs 12.4 months; median TTP-b, 7.2 vs 7.4 months). Patients receiving trastuzumab at diagnosis of BM, continuation of anti-HER2 therapy increased OS (HR, 0.53; 95% CI, 0.34-0.83; P = .005) and TTP-b (HR, 0.41; 95% CI, 0.23-0.74; P = .003); no additional benefit was seen with switching over between trastuzumab and lapatinib (median OS, 18.4 vs 22.7 months; median TTP-b: 7.4 vs 8.7 months). In conclusion, SRS or S/SRS + WBRT were equivalent for patients' OS and local control. Continuation systemic chemotherapy including anti-HER2 therapy improved OS and TTP-b with no demonstrable advantage of capecitabine and lapatinib over other agents of physicians' choice was observed.

Abstract PS15-10: Survival outcomes and prognosis for patients with triple negative breast cancer who received stereotactic radiosurgery for brain metastases

Background: Triple-negative breast cancer (TNBC) has a high propensity for brain metastasis (BM) with poor prognosis. Stereotactic radiosurgery (SRS) has emerged as an effective treatment option for BM. However, clinical outcomes after SRS for BM from TNBC have not been well defined. We evaluated survival outcomes and prognostic factors among TNBC patients who received SRS for BMs.Methods: We retrospectively reviewed 99 patients with TNBC and BM who had received SRS at a single large-volume cancer center from May 2008 through April 2018. For the initial treatment of BM, 73 patients received SRS, 25 received whole-brain radiotherapy (WBRT), and 1 patient received surgery. Endpoints were overall survival (OS) from BM diagnosis, BM progression-free survival (BMPFS) from start of BM treatment, and times to intracranial local and distant failure from start of BM treatment. Both intracranial local and distant failure were considered BM progression. Local failure was defined as an increase in size of any treated lesions on imaging or assessment of treating physicians; enlargement attributable to radiation necrosis or post-radiation change was not counted as local failure. Kaplan-Meier analysis and Cox proportional hazard regression models were used to estimate survival curves and identify prognostic factors.Results: The median follow-up time from BM diagnosis was 12.7 months (95% confidence interval [CI] 1.3–52.1). The median age at BM diagnosis was 52 (range 24-82). The median interval between the diagnosis of primary breast cancer and BM was 25.8 months (95% CI 8.7–120.3). Of the 99 patients, 81 (81.8%) had 1-3 BMs and 18 (18.2%) had &gt;3 BMs at diagnosis. The median OS time for all patients was 13.3 months (95% CI 10.3–16.4), and the cumulative survival rates were 55.1% at 1 year and 29.2% at 2 years. Factors independently associated with increased risk of death in multivariate analysis were Karnofsky performance score (KPS) ≤70 (p=0.01) and uncontrolled extracranial metastasis at BM diagnosis (p=0.05). No difference was found in OS according to type of initial treatment for BMs. Of the initial 99 patients, 12 were excluded from the evaluation of BMPFS, local and distant failure for missing follow-up imaging after initial treatment. The median BMPFS time was 7.2 months (95% CI 5.1–9.3). Of the 87 evaluable patients, 23 (26.4%) developed local recurrence after initial treatment, and among these 10 of 61 patients (16.4%) had received SRS and 13 of 25 patients (52%) had received WBRT. Patients initially treated with SRS had longer time to local failure than WBRT (50th percentile not reached vs. median 14.0 months, p=0.001). Multivariate analysis showed higher risk of local failure for patients who initially received WBRT versus SRS (hazard ratio [HR] 3.4, p=0.005). Forty-nine of 87 patients (56.3%) developed distant brain recurrence after initial treatment, and among these 35 of 61 patients (57.4%) had received SRS and 14 of 25 patients (56%) had received WBRT. No difference in risk of distant brain failure was found for patients initially treated with SRS versus WBRT (p=0.24). No difference was found in time to develop distant failure after initial treatment with SRS (median 18.4 months) versus WBRT (median 12.8 months, p=0.24).Conclusion: Patients with BM from TNBC had a median OS time of 13.3 months and a BMPFS time of 7.2 months. KPS≤70 and uncontrolled extracranial disease at the time of BM diagnosis were independent prognostic factors that increase risk of death. Patients initially treated with SRS had a longer time to develop intracranial local failure than those initially given WBRT, and this may be related to patient selection. Further prospective studies of larger numbers of patients with BM from TNBC are needed for a more accurate comparison of treatment modalities.

Citation Format: Ran An, Yan Wang, Fuchenchu Wang, Chao Gao, Akshara Singareeka Raghavendra, Diana Amaya, Nuhad K Ibrahim, Jing Li. Survival outcomes and prognosis for patients with triple negative breast cancer who received stereotactic radiosurgery for brain metastases [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS15-10.

Effect of Taxane Chemotherapy With or Without Indoximod in Metastatic Breast Cancer: A Randomized Clinical Trial

Importance

Indoleamine 2,3-dioxygenase 1 (IDO1) causes tumor immune suppression. The IDO1 pathway inhibitor indoximod combined with a taxane in patients with ERBB2-negative metastatic breast cancer was tested in a prospective clinical trial.

Objective

To assess clinical outcomes in patients with ERBB2-negative metastatic breast cancer treated with indoximod plus a taxane.

Design, Setting, and Participants

This phase 2 double-blinded randomized 1:1 placebo-controlled clinical trial enrolled patients at multiple international centers from August 26, 2013, to January 25, 2016. Eligibility criteria included ERBB2-negative metastatic breast cancer, ability to receive taxane therapy, good performance status, normal organ function, no previous immunotherapy use, and no autoimmune disease. The study was discontinued in June 2017 because of lack of efficacy. Data analysis was performed from February 2019 to April 2020.

Interventions

A taxane (paclitaxel [80 mg/m2] weekly 3 weeks on, 1 week off, or docetaxel [75 mg/m2] every 3 weeks) plus placebo or indoximod (1200 mg) orally twice daily as first-line treatment.

Main Outcomes and Measures

The primary end point was progression-free survival (PFS); secondary end points were median overall survival, objective response rate, and toxic effects. A sample size of 154 patients would detect a hazard ratio of 0.64 with 1-sided α = .1 and β = .2 after 95 events. Archival tumor tissue was stained with immunohistochemistry for IDO1 expression as an exploratory analysis.

Results

Of 209 patients enrolled, 169 were randomized and 164 were treated (85 in the indoximod arm; 79 in the placebo arm). The median (range) age was 58 (29-85) years; 166 (98.2%) were female, and 135 (79.9%) were White. The objective response rate was 40% and 37%, respectively (indoximod vs placebo) (P = .74). The median (range) follow-up time was 17.4 (0.1-39.4) months. The median PFS was 6.8 months (95% CI, 4.8-8.9) in the indoximod arm and 9.5 months (95% CI, 7.8-11.2) in the placebo arm (hazard ratio, 1.2; 95% CI, 0.8-1.8). Differences between the experimental and placebo arms in median PFS (6.8 vs 9.5 months) and overall survival (19.5 vs 20.6 months) were not statistically significant. Grade 3 or greater treatment-emergent adverse events occurred in 60% of patients in both arms.

Conclusions and Relevance

This randomized clinical trial found that, among patients with ERBB2-negative metastatic breast cancer, addition of indoximod to a taxane did not improve PFS compared with a taxane alone.

Trial Registration

ClinicalTrials.gov Identifier: NCT01792050.

A Randomized Phase II Study of Sequential Eribulin Versus Paclitaxel Followed by FAC/FEC as Neoadjuvant Therapy in Patients with Operable HER2-Negative Breast Cancer

Lessons Learned

The combination of eribulin with 5‐fluorouracil, either doxorubicin or epirubicin, and cyclophosphamide (FAC/FEC) was not superior to the combination of paclitaxel with FAC/FEC and was associated with greater hematologic toxicity.

Eribulin followed by an anthracycline‐based regimen is not recommended as a standard neoadjuvant therapy in nonmetastatic operable breast cancer.

Background

Neoadjuvant systemic therapy is the standard of care for locally advanced operable breast cancer. We hypothesized eribulin may improve the pathological complete response (pCR) rate compared with paclitaxel.

Methods

We conducted a 1:1 randomized open‐label phase II study comparing eribulin versus paclitaxel followed by 5‐fluorouracil, either doxorubicin or epirubicin, and cyclophosphamide (FAC/FEC) in patients with operable HER2‐negative breast cancer. pCR and toxicity of paclitaxel 80 mg/m² weekly for 12 doses or eribulin 1.4 mg/m² on days 1 and 8 of a 21‐day cycle for 4 cycles followed by FAC/FEC were compared.

Results

At the interim futility analysis, in March 2015, 51 patients (28 paclitaxel, 23 eribulin) had received at least one dose of the study drug and were thus evaluable for toxicity; of these, 47 (26 paclitaxel, 21 eribulin) had undergone surgery and were thus evaluable for efficacy. Seven of 26 (27%) in the paclitaxel group and 1 of 21 (5%) in the eribulin group achieved a pCR, and this result crossed a futility stopping boundary. In the paclitaxel group, the most common serious adverse events (SAEs) were neutropenic fever (grade 3, 3 patients, 11%). In the eribulin group, nine patients (39%) had neutropenia‐related SAEs, and one died of neutropenic sepsis. The study was thus discontinued. For the paclitaxel and eribulin groups, the 5‐year event‐free survival (EFS) rates were 81.8% and 74.0% (hazard ratio [HR], 1.549; 95% confidence interval [CI], 0.817–2.938; p = .3767), and the 5‐year overall survival (OS) rates were 100% and 84.4% (HR, 5.813; 95% CI, 0.647–52.208; p = .0752), respectively.

Conclusion

We did not observe a higher proportion of patients undergoing breast conservation surgery in the eribulin group than in the paclitaxel group. The patients treated with eribulin were more likely to undergo mastectomy and less likely to undergo breast conservation surgery, but the difference was not statistically significant.

As neoadjuvant therapy for operable HER2‐negative breast cancer, eribulin followed by FAC/FEC is not superior to paclitaxel followed by FAC/FEC and is associated with a higher incidence of neutropenia‐related serious adverse events.

A Practical Approach to the Management of Cancer Patients During the Novel Coronavirus Disease 2019 (COVID-19) Pandemic: An International Collaborative Group

The outbreak of coronavirus disease 2019 (COVID-19) has rapidly spread globally since being identified as a public health emergency of major international concern and has now been declared a pandemic by the World Health Organization (WHO). In December 2019, an outbreak of atypical pneumonia, known as COVID-19, was identified in Wuhan, China. The newly identified zoonotic coronavirus, severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), is characterized by rapid human-to-human transmission. Many cancer patients frequently visit the hospital for treatment and disease surveillance. They may be immunocompromised due to the underlying malignancy or anticancer therapy and are at higher risk of developing infections. Several factors increase the risk of infection, and cancer patients commonly have multiple risk factors. Cancer patients appear to have an estimated twofold increased risk of contracting SARS-CoV-2 than the general population. With the WHO declaring the novel coronavirus outbreak a pandemic, there is an urgent need to address the impact of such a pandemic on cancer patients. This include changes to resource allocation, clinical care, and the consent process during a pandemic. Currently and due to limited data, there are no international guidelines to address the management of cancer patients in any infectious pandemic. In this review, the potential challenges associated with managing cancer patients during the COVID-19 infection pandemic will be addressed, with suggestions of some practical approaches. IMPLICATIONS FOR PRACTICE: The main management strategies for treating cancer patients during the COVID-19 epidemic include clear communication and education about hand hygiene, infection control measures, high-risk exposure, and the signs and symptoms of COVID-19. Consideration of risk and benefit for active intervention in the cancer population must be individualized. Postponing elective surgery or adjuvant chemotherapy for cancer patients with low risk of progression should be considered on a case-by-case basis. Minimizing outpatient visits can help to mitigate exposure and possible further transmission. Telemedicine may be used to support patients to minimize number of visits and risk of exposure. More research is needed to better understand SARS-CoV-2 virology and epidemiology.

Prognostic impact of high stromal tumor-infiltrating lymphocytes (sTIL) in the absence of pathologic complete response (pCR) to neoadjuvant therapy (NAT) in early stage triple negative breast cancer (TNBC)

583

Background: Pathologic complete response is an excellent surrogate for disease-free survival (DFS) and overall survival (OS) in TNBC. High sTIL is associated with improved pCR rates in TNBC. Recent data suggest that high sTIL is also associated with improved outcomes in patients who received no chemotherapy for early stage TNBC (Park, Annals of Oncology, 2019). Thus, we hypothesized that high sTIL may have prognostic impact in patients who do not achieve pCR to NAT. Methods: Pretreatment core biopsies from 182 patients with early-stage TNBC enrolled on the ARTEMIS trial (NCT02276443) were evaluated for sTIL by H&E. Patients were stratified according to sTIL (low < 30%, and high > 30%) and pCR (patients with pCR vs. no pCR). The primary outcome measure was DFS, defined from the date of diagnosis to the first local recurrence, distant metastases or death. Cox proportional hazards regression model was used. During follow-up 33 events for DFS were observed. Results: Among subjects who achieve pCR, DFS was excellent regardless of sTIL status and significantly better than those without pCR (p < 0.05). However, patients with high sTIL and no pCR demonstrated significantly worse DFS compared to all subjects having pCR (HR 0.18, 95% CI 0.04-0.76, p = 0.02). Additionally, we did not find a significant difference between high and low sTIL patients who did not achieve pCR. Conclusions: In early TNBC receiving NAT, for patients failing to achieve pCR, high sTIL was not associated with improved DFS; outcomes were comparable to those with low sTIL without pCR. Thus, high sTIL at baseline does not appear to confer an intrinsic prognostic benefit in the absence of pCR.

The incidence and impact of brain metastasis in patients with hereditary BRCA1/2 mutated invasive breast cancer in a prospectively followed cohort

1096

Background: Previous reports suggest the incidence of brain metastasis is higher in patients with hereditary BRCA1 mutations compared to BRCA1 noncarriers among breast cancer patients who develop recurrent disease. PARP inhibitors are now standard therapies for metastatic breast cancer patients with germline BRCA1 or BRCA2 mutations ( gBRCA1/2) based on their efficacy in treating systemic disease. However, as management of systemic disease improves, a concern is that patients with hereditary BRCA mutations may experience higher rates of disease progression in the CNS. We aimed to estimate the incidence of brain metastasis in breast cancer patients with gBRCA1/2 using a prospectively maintained gBRCA database and to assess the impact of brain metastasis on survival. Methods: To determine incidence, we queried a prospectively maintained electronic database that included patients referred to the MDACC genetics department and who underwent gBRCA1/2 testing. We identified patients with stage I-III invasive breast cancer who were treated between 2000-2017 and assessed for disease recurrence and brain metastasis. To expand our cohort for descriptive characteristics (separate from the incidence analysis), we queried the Breast Medical Oncology database for patients with brain metastasis who had undergone BRCA1/2 testing outside the genetics department or at outside institutions. Results: Of 474 patients with Stage I-III breast cancer and gBRCA1, 77 (16.2%) developed distant metastasis (median f/u: 9.1 years). Of these patients, 34/77 (44.2%) developed brain metastasis. In comparison, 42 of 318 (13.2%) of gBRCA2 patients with Stage I-III breast cancer developed distant recurrence (median f/u: 8.4 years), and 7/42 (16.7%) experienced brain metastasis. In gBRCA1 patients with brain metastasis, 45/48 (83.8%) had triple negative disease, and the median time from diagnosis to brain metastasis was 2.45 years. The brain was among the initial sites of disease recurrence in 24/48 (50%) of gBRCA1 patients. For gBRCA1 patients with distantly recurrent disease, median OS from diagnosis was 3.19 years for patients with brain metastasis vs. 5.37 years for patients without brain mets (HR 0.54; 95% CI 0.34 to 0.85; P = 0.0082). Conclusions: Brain metastasis is frequent among breast cancer patients with recurrent disease and hereditary BRCA1 mutations. Development and testing of agents with intracranial activity is critical for improving long-term outcomes in gBRCA1 patients with metastatic breast cancer.

Systemic therapy for patients with breast cancer and one to three brain metastases (BM)

1090

Background: Despite advances in systemic therapies and improved overall survival of metastatic breast cancer (MBC) patients, the development of brain metastases (BMs) remains a challenging complication that affects quality of life and increases morbidity and mortality. Current clinical practice guidelines recommend local treatment of BMs without changing systemic therapy (CST) in patients with stable systemic disease. Methods: We retrospectively investigated the impact of CST (when applicable as per treating physician’s discretion) after diagnosis of the initial 1-3 BMs on the patient’s progression-free survival time (PFS), defined as time to death, to a second BMs or to extracranial metastases. All MBC patients with 1 to 3 BMs only (without extracranial disease) treated at our institution between 2002 and 2017 were identified. For each patient, full information on follow-up and administered therapies were mandatory for inclusion. Hazard ratios (HR) were calculated using the Cox proportional hazard model. We also computed the restricted mean survival time (RMST) up to 5 years of follow-up. Results: Among the 2645 patient with BM treated at our institution, 80 were included for analysis. In regards to primary BMs management in patients, 46 of 80 (57%) were treated by radiation therapy, 6 of 80 (7.5%) underwent surgical resection, and 28 of 80 (35%) were managed by a combination of surgery and radiation therapy. All patients had staging imaging documenting lack of extracranial metastases at the time of local therapy of BMs. Following the primary management of BM, we observed that providers changed systemic therapy in 32 of 80 (40%), defined as the CST group. CST included both initiation of therapy in 16 of 80 (20%) and switching of adjuvant therapy in 16 of 80 (20%). Median PFS among CST was 7.7 months vs. 7.2 months among no CST (HR = 0.855, 95% confidence interval (CI) 0.53-1.38, p = 0.52). 5-year RMST for the CST group was 16.6 months vs. 12.8 months in no CST group. The difference of 3.8 months (95% CI 4.3-11.8) was not statistically significant. Conclusions: Patients with 1-3 BMs without extracranial disease had a median PFS close to 7.5 months after local therapy. Consistent with current standard of care of maintaining the same systemic therapy approach upon developing isolated BMs, our findings did not demonstrate a significant difference in PFS between patients who experienced a change in systemic therapy compared to those who did not.

In Reply

This letter to the editor remarks on additional considerations for the management of febrile neutropenia during the COVID‐19 pandemic, in response to the letter by Boutayeb et al.

Abstract P1-19-18: Everolimus, letrozole and trastuzumab in hormone receptor-positive, HER2-positive/amplified or mutant metastatic cancer: Evaluating synergy and overcoming resistance

Background: Combinations of HER2 and aromatase or mTOR inhibitors demonstrated activity in the clinical setting. We hypothesized that the triple combination of HER2 targeted therapy, aromatase and mTOR inhibitor has increased anticancer activity.

Methods: We designed a 3+3 dose escalation phase I study of the aromatase inhibitor letrozole 2.5mg PO daily, mTOR inhibitor everolimus 2.5-10mg PO daily and HER2 antibody trastuzumab 4-8mg loading dose followed by 2-4mg maintenance dose IV on day 1 of 21-day cycle in patients with hormone-receptor positive, HER2-positive/amplified or mutant advanced cancers (confirmed by immunohistochemistry and/or FISH and/or next-generation sequencing) with preplanned expansion cohort at for patients with metastatic breast cancer to determine maximum tolerated dose (MTD) and/or recommended phase 2 dose (RP2D), dose limiting toxicities (DLT), overall safety and response (NCT02152943).

Results: A total of 32 patients (men, 1; women, 31; HER2 amplification, 28; HER2 mutation, 4; breast cancer, 26; other cancers, 6), median age 55.5 years, median of 5 prior therapies (including letrozole [13] or other aromatase inhibitor [10]; everolimus [3]; trastuzumab [25] or other HER2 targeted therapy [2]) were enrolled in the planned 6 dose levels. The MTD has not been reached and letrozole 2.5mg PO daily, everolimus 10mg PO daily and trastuzumab 8mg loading dose followed by 4mg maintenance dose IV on day 1 of 21-day cycle was declared as RP2D. DLTs included grade 3 (G3) mucositis (1 patient) at dose level 3, and G3 thrombocytopenia, neutropenia (1 patient) at dose level 4. Other G3 or G4 treatment-related toxicities included G4 hyperglycemia in 1 patient, G3 hyperglycemia in 3 patients, G4 anemia in 1 patient, G3 anemia in 2 patients, G3 thrombocytopenia in 1 patient, G3 transaminitis in 1 patient, G3 mucositis in 1 patient and G3 headache in 1 patient. Of 32 patients, 5 (16%) had a partial response (all with heavily-pretreated breast cancer with HER2 amplification [4] or HER2A775_G776insYVMA mutation [1]), 23 (72%) stable disease (SD) including 5 (16%) patients with SD &gt; 12 months (all with heavily-pretreated breast cancer) and 4 (13%) progressed. The median change in size of target lesions per RECIST 1.1. was -5% (-91% to +47%). Median time to treatment failure (TTF) was 4.3 months (95% CI 0.0-9.6). A total of 14 patients had serial plasma collection to assess dynamics of circulating tumor DNA and clonal evolution and the data will be presented at the meeting.

Conclusions: The combination of letrozole, everolimus and trastuzumab is well tolerated with encouraging activity in heavily-pretreated patients with HER2-amplified or mutant advanced breast cancer.

Citation Format: Alexej Ballhausen, Jennifer J Wheler, Daniel D Karp, Sarina A Piha-Paul, Siqing Fu, Shubham Pant, Apostolia M Tsimberidou, David S Hong, Vivek Subbiah, Veronica R Holley, Helen J Huang, Abeena M Brewster, Kimberly H Koenig, Nuhad K Ibrahim, Funda Meric-Bernstam, Filip Janku. Everolimus, letrozole and trastuzumab in hormone receptor-positive, HER2-positive/amplified or mutant metastatic cancer: Evaluating synergy and overcoming resistance [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P1-19-18.

Phase II study of Radium-223 dichloride combined with hormonal therapy for hormone receptor-positive, bone-dominant metastatic breast cancer

Background

Radium‐223 dichloride (Ra‐223) is a targeted alpha therapy that induces localized cytotoxicity in bone metastases. We evaluated the efficacy and safety of Ra‐223 plus hormonal therapy in hormone receptor‐positive (HR+), bone‐dominant metastatic breast cancer.

Methods

In this single‐center phase II study, 36 patients received Ra‐223 (55 kBq/kg intravenously every 4 weeks) up to 6 cycles with endocrine therapy. The primary objective was to determine the clinical disease control rate at 9 months. Secondary objectives were to determine (a) tumor response rate at 6 months, (b) progression‐free survival (PFS) durations, and (c) safety.

Results

The median number of prior systemic treatments for metastatic disease was 1 (range, 0‐4). The disease control rate at 9 months was 49%. The tumor response rate at 6 months was 54% (complete response, 21%; partial, 32%). The median PFS was 7.4 months (95% CI, 4.8‐not reached [NR]). The median bone‐PFS was 16 months (95% CI, 7.3‐NR). There were no grade 3/4 adverse events.

Conclusions

Ra‐223 with hormonal therapy showed possible efficacy in HR+ bone‐dominant breast cancer metastasis, and adverse events were tolerable. We plan to further investigate the clinical application of Ra‐223 in these patients. (NCT02366130).

Abstract 323: Combined inhibition of STAT-3 & DNA repair in palbociclib resistant breast cancer

The CDK4/6 inhibitor palbociclib is currently being used in combination with endocrine therapy to treat advanced ER positive breast cancer patients. While this treatment has shown great promise in the clinic, about 25-35% of the patients do not respond initially, and almost all patients eventually acquire resistance. Hence, understanding the mechanisms of acquired resistance to CDK4/6 inhibition is crucial to devise alternate treatment strategies.

To identify mechanisms of resistance to CDK4/6 inhibition we developed MCF-7 and T47D palbociclib resistant cells in a step-wise manner by gradually increasing concentrations of palbociclib. These cells are not only resistant to palbociclib, but exhibited resistance to the other approved CDK4/6 inhibitors; ribociclib and abemaciclib. Additionally, we assessed if these resistant cells have an altered response to endocrine therapy and observed that these cells are also resistant to treatment with tamoxifen or fulvestrant by about 16-fold. Multi-omics analyses revealed enrichment of pathways known to regulate EMT and promote stem-like properties, as well as, downregulation of estrogen response and DNA repair pathways.

Palbociclib resistant cells exhibited mammosphere formation and CD44high/CD24low population indicating the presence of increased breast cancer stem cell-like cells (B-CSC-L). Given the recently elucidated role of IL-6/STAT-3 mediated B-CSC-L phenotypes in drug resistance, we examined IL-6 mRNA levels, which increased by &gt;12-fold in the resistant cells. Treatment with STAT-3 inhibitors, napabucasin and C188-9, significantly decreased the B-CSC-L population and mammosphere formation, indicating a crucial role for the IL-6/STAT-3 pathway in driving B-CSC-L phenotype and palbociclib resistance.

Since DNA repair pathways were collectively downregulated in the palbociclib resistant cells, we examined their sensitivity to DNA damaging agents. Results showed that resistant cells were more sensitive to olaparib (PARP inhibition), with no effect on B-CSC-L population. Next, we examined if combined treatment with agents targeting STAT-3 and PARP would be synergistic in palbociclib resistant cells. Results show that combined treatment with olaparib and napabucasin or C-1889 significantly decreased B-CSC-L population, colony formation and increased cell death via apoptosis, when compared to no-treatment or single treatment controls of the palbociclib resistant cells.

Lastly, we interrogated matched tumor samples from breast cancer patients who progressed on palbociclib for deregulation of estrogen receptor, DNA repair, and IL-6/STAT3 signaling and found that these pathways are altered as compared to the pre-treatment samples.

Taken together, the results show that targeting IL-6/STAT-3 mediated cancer stem cells and DNA repair deficiency by PARP inhibitors in combination can effectively treat acquired resistance to palbociclib.

Citation Format: Nicole M. Kettner, Smruthi Vijayaraghavan, Merih Guray Durak, Tuyen Bui, Mehrnoosh Kohansal, Min Jin Ha, Bin Liu, Xiayu Rao, Jing Yang, Min Yi, Jason P. Carey, Xian Chen, T. Kris Eckols, Akshara S. Raghavendra, Nuhad K. Ibrahim, Meghan Karuturi, Stephanie S. Watowich, Aysegul A. Sahin, David J. Tweardy, Kelly K. Hunt, Debu Tripathy, Khandan Keyomarsi. Combined inhibition of STAT-3 & DNA repair in palbociclib resistant breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 323.

Combined Inhibition of STAT3 and DNA Repair in Palbociclib-Resistant ER-Positive Breast Cancer

PURPOSE

Cyclin-dependent kinase 4/6 (CDK4/6) inhibitors are currently used in combination with endocrine therapy to treat advanced hormone receptor-positive, HER2-negative breast cancer. Although this treatment doubles time to progression compared with endocrine therapy alone, about 25%-35% of patients do not respond, and almost all patients eventually acquire resistance. Discerning the mechanisms of resistance to CDK4/6 inhibition is crucial in devising alternative treatment strategies.

EXPERIMENTAL DESIGN

Palbociclib-resistant cells (MCF-7 and T47D) were generated in a step-wise dose-escalading fashion. Whole-exome sequencing, genome-wide expression analysis, and proteomic analysis were performed in both resistant and parental (sensitive) cells. Pathway alteration was assessed mechanistically and pharmacologically. Biomarkers of altered pathways were examined in tumor samples from patients with palbociclib-treated breast cancer whose disease progressed while on treatment.

RESULTS

Palbociclib-resistant cells are cross-resistant to other CDK4/6 inhibitors and are also resistant to endocrine therapy (estrogen receptor downregulation). IL6/STAT3 pathway is induced, whereas DNA repair and estrogen receptor pathways are downregulated in the resistant cells. Combined inhibition of STAT3 and PARP significantly increased cell death in the resistant cells. Matched tumor samples from patients with breast cancer who progressed on palbociclib were examined for deregulation of estrogen receptor, DNA repair, and IL6/STAT3 signaling, and results revealed that these pathways are all altered as compared with the pretreatment tumor samples.

CONCLUSIONS

Palbociclib resistance induces endocrine resistance, estrogen receptor downregulation, and alteration of IL6/STAT3 and DNA damage response pathways in cell lines and patient samples. Targeting IL6/STAT3 activity and DNA repair deficiency using a specific STAT3 inhibitor combined with a PARP inhibitor could effectively treat acquired resistance to palbociclib.

The impact of smoking cessation on breast cancer patients’ survival

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Background: Breast cancer remains to be one of the highest causes of cancer mortality amongst females globally, second only to lung cancer. Smoking is strongly associated with increased all-cause mortality, including breast cancer related death. It has also been shown to have a negative influence on long-term survival after successful breast cancer treatment. Prior studies have shown that smoking cessation may lead to improved prognosis and better outcomes. Methods: This is a retrospective cohort study of breast cancer patients who were identified as smokers, some of who were referred to the tobacco treatment program (TTP) located at MD Anderson Cancer Center. TTP includes careful patient screening, motivational counseling, and pharmacotherapy. We complemented the original data collected by conducting in-depth chart reviews to extract data including patient demographics, date of diagnosis, stage of cancer, smoking status, duration of abstinence and dates of follow-up or death. We then examined associations between smoking status and survival status using multinomial regression models adjusting for biomarkers of disease and personal characteristics. Results: Among all breast cancer patients (N = 31069), we identified those who are smokers (n = 2320) by matching the TTP database with smoking status from our institutional electronic health records. Of those, 740 patients were referred to TTP. Amongst these, 242 patients quit smoking and remained abstinent at the 9 month follow-up. Compared with non-abstainers, those who quit were more likely to be alive with no evidence of disease during the observation time (RR = 1.62, p = 0.045). When analyzed at different stages, the RR went from 1.35 (p = 0.42) to 2.77 (p = 0.34) for stages 3 and 1, respectively. Although the strength of this relationship varied among disease stage, the direction of the relationship remain consistent. Conclusions: Our data shows that smoking cessation is associated with improved survival status amongst breast cancer survivors across all stages. Comprehensive smoking cessation services may improve survivorship when started as early as the time of diagnosis. Further analysis of the association between smoking cessation and other associated medical outcomes will be conducted to further determine the specific impact of cessation programs.

Brain metastasis in patients with hereditary BRCA-mutated invasive breast cancer

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Background: In the past six months, two poly(ADP-ribose) polymerase (PARP) inhibitors have been approved for the treatment of patients with metastatic breast cancer and germline pathogenic variants in BRCA1 or BRCA2 ( gBRCA). In addition, recent data from the IMpassion 130 trial lends support for the role of immunotherapy in a subset of patients with triple negative breast cancer (TNBC). Approximately 60% of patients with gBRCA1 have TNBC. There is evidence that both PARP inhibitors and checkpoint inhibitors cross the blood-brain barrier and both classes of agents have entered clinical trials for patients with brain metastases in other tumor types. We studied the clinical course of breast cancer patients with gBRCA and brain metastasis at our institution to inform clinical trial design for this group of patients with poor outcomes. Methods: Patients with stage I to III invasive breast cancer, gBRCA, and eventual development of brain metastasis were identified from clinical databases. Data analyzed included breast cancer subtype and stage at diagnosis, treatment, time to distant recurrence and to discovery of brain metastasis, and overall survival from time of development of brain metastasis. Results: Patients in our cohort (n = 24, to date) were diagnosed at a young age (median age 39) and primarily had TNBC (21/24, 87.5%) with infiltrating ductal carcinoma histology. Nineteen patients had gBRCA1 and 4 patients had gBRCA2. All but 1 patient received anthracycline-based chemotherapy in the neoadjuvant/adjuvant setting. Median time to distant metastasis was 2 years (range: 0.8 – 15) and the brain was the first site of recurrence in 5 of 24 (21%) patients. Median time from diagnosis to development of brain metastasis was 2.6 years (range: 1.2 – 19) and most patients (18/25, 72%) had multiple brain metastases discovered on the initial brain MRI. Median overall survival (OS) was 3.7 years (range: 1.8 – 24) and median OS from the time of brain metastasis was 7 months (range: 1 month – 13 years). Conclusions: Breast cancer patients with germline pathogenic variants in BRCA1/2 who develop brain metastasis have a dismal prognosis. These patients may benefit from an agent with intracranial activity at the time of first distant recurrence.

Beyond TILs: Predictors of pathologic complete response (pCR) in triple-negative breast cancer (TNBC) patients with moderate tumor-infiltrating lymphocytes (TIL) receiving neoadjuvant therapy

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Background: Increased TIL in TNBC is associated with higher rates of pCR. High TIL is also associated with improved disease free survival and overall survival. The aim of this study is to identify data cut-points of pre-treatment low, moderate and high TIL count based on pCR and to identify clinical and pathological predictors of pCR in patients with moderate TIL. Methods: We evaluated the relationship between pCR and TIL in 180 patients with stage I-III TNBC enrolled in the ARTEMIS trial (NCT02276443). Recursive portioning was used to identify cut-points. Clinical and pathological variables such as age at diagnosis, stage, race, histology as well as Ki-67, vimentin, and androgen receptor (AR) by immunohistochemistry, were evaluated in pts with moderate TIL. A multivariable logistic regression model identified variables independently, significantly associated with pCR. Results: Four TIL groups were identified with pCR rates of 23%, 31%, 48% and 78% respectively (p < 0.0001) (Table A). In the two combined moderate TIL groups, 90 (97%) pts were evaluable for the multivariate model. Stage I-II disease, high Ki-67 and low AR were associated with increased probability of pCR (Table B). The multivariable logistic regression model area under the ROC curve was 0.78 (95% CI=0.68-0.88; p<0.0001). A model of computed risk score [ Stage I-II (score 2)+Ki-67≥ 50% (score 1)+AR<10% (score 1)] predicted a probability of 67% for pCR when all three variables were favorable (Table). Conclusions: Four TIL groups were identified. In pts with moderate TIL levels, early stage disease, high Ki-67 and low AR were associated with increased probability of pCR with neoadjuvant therapy. [Table: see text]

A phase Ib study of entinostat plus lapatinib with or without trastuzumab in patients with HER2-positive metastatic breast cancer that progressed during trastuzumab treatment

BACKGROUND

Human epidermal growth factor 2 (HER2) is an effective therapeutic target in breast cancer; however, resistance to anti-HER2 agents such as trastuzumab and lapatinib develops. In a preclinical model, an HDAC inhibitor epigenetically reversed the resistance of cancer cells to trastuzumab and showed synergistic efficacy with lapatinib in inhibiting growth of trastuzumab-resistant HER2-positive (HER2+) breast cancer.

METHODS

A phase 1b, dose escalation study was performed to assess maximum tolerated dose, safety/toxicity, clinical efficacy and explored pharmacodynamic biomarkers of response to entinostat combined with lapatinib with or without trastuzumab.

RESULTS

The combination was safe. The MTD was lapatinib, 1000 mg daily; entinostat, 12 mg every other week; trastuzumab, 8 mg/kg followed by 6 mg/kg every 3 weeks. Adverse events included diarrhoea (89%), neutropenia (31%), and thrombocytopenia (23%). Neutropenia, thrombocytopenia and hypokalaemia were noted. Pharmacodynamic assessment did not yield conclusive results. Among 35 patients with evaluable response, PR was observed in 3 patients and CR in 3 patients, 1 maintained SD for over 6 months.

DISCUSSION

This study identified the MTD of the entinostat, lapatinib, and trastuzumab combination that provided acceptable tolerability and anti-tumour activity in heavily pre-treated patients with HER2+ metastatic breast cancer, supporting a confirmatory trial.

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.

Profiles of brain metastases: Prioritization of therapeutic targets

We sought to compare the tumor profiles of brain metastases from common cancers with those of primary tumors and extracranial metastases in order to identify potential targets and prioritize rational treatment strategies. Tumor samples were collected from both the primary and metastatic sites of nonsmall cell lung cancer, breast cancer and melanoma from patients in locations worldwide, and these were submitted to Caris Life Sciences for tumor multiplatform analysis, including gene sequencing (Sanger and next-generation sequencing with a targeted 47-gene panel), protein expression (assayed by immunohistochemistry) and gene amplification (assayed by in situ hybridization). The data analysis considered differential protein expression, gene amplification and mutations among brain metastases, extracranial metastases and primary tumors. The analyzed population included: 16,999 unmatched primary tumor and/or metastasis samples: 8,178 nonsmall cell lung cancers (5,098 primaries; 2,787 systemic metastases; 293 brain metastases), 7,064 breast cancers (3,496 primaries; 3,469 systemic metastases; 99 brain metastases) and 1,757 melanomas (660 primaries; 996 systemic metastases; 101 brain metastases). TOP2A expression was increased in brain metastases from all 3 cancers, and brain metastases overexpressed multiple proteins clustering around functions critical to DNA synthesis and repair and implicated in chemotherapy resistance, including RRM1, TS, ERCC1 and TOPO1. cMET was overexpressed in melanoma brain metastases relative to primary skin specimens. Brain metastasis patients may particularly benefit from therapeutic targeting of enzymes associated with DNA synthesis, replication and/or repair.

Developing anti-HER2 vaccines: Breast cancer experience

Breast cancer accounts for more than one million new cases annually and is the leading cause of death in women globally. HER2 overexpression induces cellular and humoral immune responses against the HER2 protein and is associated with higher tumor proliferation rates. Trastuzumab-based therapies are effectively and widely used as standard of care in HER2-amplified/overexpressed breast cancer patients; one cited mechanism of action is the induction of passive immunity and antibody-dependent cellular cytotoxicity against malignant breast cancer cells. These findings drove the efforts to generate antigen-specific immunotherapy to trigger the patient's immune system to target HER2-overexpressing tumor cells, which led to the development of various vaccines against the HER2 antigen. This article discusses the various anti-HER2 vaccine formulations and strategies and their potential role in the metastatic and adjuvant settings.

Effect of neoadjuvant chemotherapy regimen on relapse-free survival among patients with breast cancer achieving a pathologic complete response: an early step in the de-escalation of neoadjuvant chemotherapy

Background

Patients with breast cancer who have a pathologic complete response (pCR) to neoadjuvant chemotherapy (NACT) have improved survival. We hypothesize that once pCR has been achieved, there is no difference in subsequent postsurgical recurrence-free survival (RFS), whichever NACT regimen is used.

Methods

Data from patients with breast cancer who achieved pCR after NACT between 1996 and 2011 were reviewed. RFS was estimated by the Kaplan-Meier method, and differences between groups were assessed using log-rank testing. Cox proportional hazards regression analysis adjusted for age, menopausal status, stage, grade, tumor subtype, and adjuvant endocrine HER2-targeted radiation treatment.

Results

Among 721 patients who achieved pCR after NACT, 157 (21.8%) were hormone receptor-positive (HR), 310 (43.3%) were HER2-amplified, and 236 (32.7%) were triple-negative; 292 (40.5%) were stage IIA, 153 (21.2%) were stage IIB, 78 (10.8%) were stage IIIA, 66 (9.2%) were stage IIIB, and 132 (18.3%) were stage IIIC. Most patients (367 [50.9%]) had been treated with adriamycin-based chemotherapy plus taxane (A + T), 56 (7.8%) without taxane (A no T), 227 (31.5%) with HER2-targeted therapy, and 71 (9.8%) provider choice. Median follow-up was 7.1 years. Adjuvant chemotherapy was employed in 196 (27%) patients, adjuvant endocrine in 261 (36%), and adjuvant radiation in the majority (559 [77.5%]). There was no statistically significant difference in RFS by NACT group. Adjusted RFS hazard ratios, comparing each treatment with the reference group A + T, were 1.25 (95% CI 0.47–3.35) for A no T, 0.90 (95% CI 0.37–2.20) for HER2-targeted therapy, and 1.28 (95% CI 0.55–2.98) for provider choice.

Conclusions

These data suggest that postsurgical RFS is not significantly influenced by the choice of NACT or cancer subtype among patients achieving pCR.

Electronic supplementary material

The online version of this article (10.1186/s13058-018-0945-7) contains supplementary material, which is available to authorized users.

Development of CNS metastases and survival in patients with inflammatory breast cancer

BACKGROUND

Inflammatory breast cancer (IBC) is associated with a poor prognosis and high risk of central nervous system (CNS) metastases.

METHODS

We retrospectively reviewed stage III-IBC patients compared with noninflammatory invasive ductal carcinoma (NI-IDC) patients treated between January 1, 1984, and December 31, 2011, who began primary treatment within 1 year of diagnosis and had been followed up for at least 1 year before the development of CNS metastasis or death. Cumulative CNS metastasis incidence and post-CNS metastasis overall survival (OS) estimates were computed. Multivariable Cox proportional hazard models explored factors for post-CNS metastasis survival.

RESULTS

A total of 2323 patients were identified (589-IBC/1734-NI-IDC). Eighty-one IBC patients developed CNS metastasis, versus 154 NI-IDC patients. The 2-, 5-, and 10-year cumulative CNS metastasis incidence rates in IBC and NI-IDC were 9.8%, 15.8%, 17.4% and 6.5%, 10.1%, and 12.7%, respectively. This was significantly different between IBC and NI-IDC patients (P = .0037). Multicovariate competing risk regression models in IBC and NI-IDC patients showed no statistically significant associations with the risk of developing CNS metastasis, except neoadjuvant taxane use in NI-IDC patients (hazard ratio, 0.45; 95% confidence interval, 0.24-0.83; P = .011). The median follow-up was 7.2 years, and the median post-CNS metastasis OS was not significantly different between IBC (7.6 months) and NI-IDC (5.6 months) patients. One hundred ninety patients with CNS metastasis died. HER2-positive patients had better OS, with a median 14.1 versus 4.3 months (P < .0001). Age >50 years (P = .012) but not IBC status was a significant predictor of post-CNS metastasis survival.

CONCLUSION

IBC patients demonstrated higher CNS metastasis incidence rates but OS following CNS metastases is similar in both groups. HER2 status and age may play prognostic roles. Cancer 2018;124:2299-305. © 2018 American Cancer Society.

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 P1-16-02: 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 P6-03-04: Central nervous system miliary metastasis in breast cancer patients

Background: Little is known regarding central nervous system (CNS) miliary metastasis (MiM), which was first described as “carcinomatous encephalitis” by Madow and Alpers in 1951. The majority of reported cases arise from primary lung and gastrointestinal adenocarcinomas, with occasional melanoma primaries and one reported case in breast cancer. Moreover, clinicopathologic correlates, disease outcomes and prognostic factors in these patients are poorly understood. Although identified most frequently on neuroimaging, radiographic criteria to objectively diagnose MiM do not exist. In this analysis of patients with brain metastasis from primary breast cancer, we propose objective, stringent radiographic criteria for CNS MiM diagnosis and identify clinicopathologic factors contributing to disease outcomes.

Methods: Using a prospectively maintained electronic database, 1,002 female patients diagnosed with brain metastasis from primary breast cancer between 2000 and 2015 were identified. Only patients with neuroimaging available for direct review (CT or MRI) were included. Our radiographic criteria for MiM diagnosis were: 1) ≥20 metastatic lesions per image slice on ≥2 noncontiguous image slices by MRI, or 2) ≥10 lesions per image slice on ≥2 noncontiguous image slices by CT, and 3) MiM lesions were required to be present bilaterally and in both the supra- and infratentorial compartments. These criteria were established upon direct review of all neuroimaging by a neuroradiologist. Number and anatomic distribution of metastatic lesions were the patterns best observed to identify cases of CNS MiM on case review; lesion size was not a reliable pattern for MiM identification. Log rank tests were used for statistical analyses.

Results: Using stringent criteria, 486 patients were included in this analysis. Twenty patients with MiM were identified (4.1%). Ten patients were diagnosed with MiM at initial brain metastasis presentation; 10 developed MiM after known brain metastasis. Biomarker based subtype distribution was as follows: HR-/HER2- (TNBC) (n=8), HR+/HER2+ (n=3), HR+/HER2- (n=4), HR-/HER2+ (n=4), unknown (n=1).

Table 1: Disease Outcomes Based on Biomarker SubtypeBiomarker SubtypeMedian Time to MiM (months) (p=0.104)Median Survival after MiM (months) (p=0.008)TNBC (n=8)32.3 (12.1-132.5)1.8 (0.5-4.0)HR+/HER2+ (n=3)44.2 (33.2-71.5)10.8 (10.2-13.3)HR+/HER2- (n=4)110.2 (23.0-156.0)4.8 (0.8-9.8)HR-/HER2+ (n=4)27.1 (3.7-39.4)4.0 (1.8-5.0)All* (n=20)37.4 (3.7-156.0)3.7 (0.4-12.3)Key: BM: Brain metastasis; * Includes 1 patient with unknown subtype.

Conclusions: Reports of MiM consist overwhelmingly of lung and gastrointestinal adenocarcinoma primaries. This retrospective, observational study is the first to establish that CNS MiM occurs in breast cancer with an incidence of roughly 4%. Review of an additional 1,600 patient charts is underway, but this preliminary study is the first to identify clinicopathologic correlates and determine disease outcomes in patients with MiM; it is also the first to propose stringent radiographic criteria for the diagnosis of CNS MiM, and further updated data will be presented at the meeting.

Citation Format: Bashour SI, Ibrahim NK, Schomer DF, Colen RR, Sawaya R, Suki D, Rao G, Murthy RK, Moulder SL, Abugabal Y, Hess KR, Fuller GN. Central nervous system miliary metastasis in breast cancer patients [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 P6-03-04.

Rapid Breast Cancer Disease Progression Following Cyclin Dependent Kinase 4 and 6 Inhibitor Discontinuation

Background: CDK 4 and 6 inhibitors (CDK4/6i), which arrest unregulated cancer cell proliferation, show clinical efficacy in breast cancer. Unexpectedly, a patient treated on a CDK4/6i-based trial, as first-line therapy in metastatic breast cancer, developed rapid disease progression following discontinuation of study drug while receiving standard second-line therapy off trial. We thus sought to expand this observation within a population of patients treated similarly at The University of Texas MD Anderson Cancer Center.

Methods: Using an IRB-approved protocol, 4 patients previously enrolled on CDK4/6i trials were analyzed for outcomes after discontinuing study drug. These patients were treated on a randomized trial of first-line endocrine therapy +/- a CDK4/6i. Rapid disease progression was defined as progression occurring within 4 months of CDK4/6i discontinuation.

Results: In total, 4 patients developed rapid disease progression and died; 2 of whom died within 6 months of CDK4/6i discontinuation.

Conclusion: This case series suggests a potential for rapid disease progression following CDK4/6i discontinuation. However, the clinical course following progression must be validated in large CDK4/6i clinical trials and standard-of-care cohorts. If confirmed, such observations may alter the algorithm for subsequent therapy in patients with disease progression on CDK4/6i. Nevertheless, the need remains to define a mechanistic basis for this rapid progression and formulate alternative therapeutic strategies.

Effect of neoadjuvant chemotherapy regimen choice in patients with breast cancer with pathologic complete response

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Background: Breast cancer patients with a pathologic complete response (pCR) to neoadjuvant chemotherapy (NACT) have improved survival. We hypothesize there is no difference in post-surgical recurrence free survival (RFS) between regimens used if pCR has been achieved. Methods: Breast cancer patients treated with NACT (using various regimens) between 1996 and 2011 who achieved pCR were examined, using a prospectively maintained electronic database. RFS was estimated by Kaplan-Meier method, differences between groups assessed using log-rank test. Cox proportional hazards regression analysis adjusted for age, menopausal status, stage, grade, tumor subtype, and adjuvant treatments. Results: 721 patients were identified: 40.4% Stage IIA, 21.2% IIB, 10.8% IIIA, 9.2% IIIB, 18.3% IIIC. 21.8% were hormone receptor positive (HR), 43.3% HER2 amplified, 32.7% triple negative. 50.9% of patients were treated with adriamycin-based chemotherapy plus taxane (adriamycin+taxane), 7.8% without taxane (adriamycin-taxane), 31.5% HER2 targeted therapy, and 9.8% provider choice. Median follow up was 7.4 years. There was no significant difference in RFS by treatment group (table 1). Adjusted RFS hazard ratios comparing each treatment to adriamycin+taxane were 1.25 (95% confidence interval 0.47-3.35) adriamycin-taxane, 0.90 (CI 0.37-2.20) HER2 targeted, and 1.28 (CI 0.55-2.98) provider choice. Conclusions: These data suggest that post-surgical RFS among patients with pCR is not significantly influenced by the type of NACT. Meta-analysis of randomized trial data should be explored to evaluate these findings. If RFS of pCR patients is not affected by regimen, this could allow flexibility in treatment choice and length. [Table: see text]