Abstract 1773: Overcoming paclitaxel resistance in triple-negative breast cancer using a novel barcoding technology

Triple-negative breast cancer (TNBC) is an aggressive breast cancer subtype for which chemotherapy remains a part of standard treatment. Although pathologic complete response (pCR) after neoadjuvant chemotherapy, including paclitaxel (PTX), is associated with good outcomes, 50-60% of TNBC patients do not experience pCR and suffer poor long-term outcomes, often due to chemotherapy resistance. Identifying and analyzing the tumor cells responsible for chemotherapy resistance will lead to improved treatment strategies.

We developed a model of TNBC resistance to neoadjuvant PTX using Met1 murine mammary carcinoma cells. To study clonal dynamics in response to PTX we developed a barcoding method, SunCatcher. First, 31 single-cell derived clonal populations were generated from parental Met1 cells. Each clone was infected with a lentiviral vector containing a unique DNA barcode detectable by qPCR. All barcoded clones (BCs) were mixed in equivalent numbers to generate a BC pool that we confirmed captures the parental Met1 heterogeneity and tumor growth kinetics.

First, PTX responses were tested in vitro. The BC pool had an IC50 of ~100 nM, while individual BCs ranged in IC50 from 5 nM to 25 µM. We maintained the BC pool in 100 nM PTX for 39 days (termed long-term PTX; LTP), at which point it became clonal for BC25, suggesting that BC25 (IC50 of 100 nM) is uniquely PTX resistant, despite being the most proliferative and Zeb1hi/EpCAMlow clone in vitro. BC25 was not detected in the control-treated BC pool at 39 days.

Next, the BC pool was orthotopically injected into FVB/NJ mice and treated the mice with 20 mg/kg PTX on days 7, 11, and 15. At the day 18 experimental endpoint, tumor volume significantly decreased by 56% in response to PTX compared to control. BC25 composition increased from 7.7% (controls) to 15% (PTX treated) within the tumors at endpoint. We also injected BC25 and LTP cells alone and administered the same PTX regimen once tumors reached 50 mm3. Both BC25 and LTP tumors were unresponsive to PTX and had a longer latency period (35d) than BC pool (10d).

We performed a drug screen of 2313 compounds spanning FDA-approved cancer therapeutics on the LTP cells to identify compounds to target the PTX-resistant clone. HDAC inhibitors were the most potent class of hits and one, Panobinostat, killed LTP cells with an IC50 of 4.3 nM.

Utilizing SunCatcher, we identified a unique PTX-resistant TNBC subclone that represents residual disease associated with poor long-term outcome. Typical in vivo experiments would have reached ethical endpoint before BC25 had a chance to grow, given its long latency, therefore this PTX-resistant clone would not have been identified. This is an important finding because therapeutic resistance can emerge after a protracted period, longer than typical pre-clinical experiments. Further work will explore mechanisms of resistance and the potential for combination therapies to prevent recurrent disease.

Citation Format: Milos Spasic, Qiuchen Guo, Adam Maynard, Gregory Goreczny, Adrienne Waks, Sara Tolaney, Elizabeth Mittendorf, Sandra McAllister. Overcoming paclitaxel resistance in triple-negative breast cancer using a novel barcoding technology [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1773.

Abstract 66: A multi-institution examination of concordance in spatial transcriptomics using the GeoMx Cancer Transcriptome Atlas

Multiplexed spatial profiling can enable biological insights by characterizing gene expression within discrete physical locations of a tissue. However, these advanced techniques can be confounded by variability of sample collection, storage, or profiling protocols, making it difficult to accurately compare data generated by different laboratories. Further, as more spatial profiling datasets become publicly available, having methods to enable meta-analysis of samples collected on different studies will maximize the learnings to support the advancement of treatments or identifying patient segments.

To quantify the variability of spatial profiling data at different laboratories and to advance data normalization methodologies, 4 independent laboratories used the NanoString® GeoMx® Digital Spatial Profiling (DSP) to profile serial 5 µm sections of tissue and cell pellet arrays (CPAs). GeoMx DSP enables high throughput, spatially resolved analysis of gene or protein expression from fresh or archival human tissues. In this study, the GeoMx Cancer Transcriptome Atlas was used to profile >1800 genes simultaneously. We examined the concordance of GeoMx data generated in the different laboratories when controlling for methodical variation (e.g., reagents, tissue source) and experimentally varying region of interest (ROI) size, collection site, and sample preservation methods.

Sections of tonsil, colon, and 2 CPAs were profiled separately at the 4 laboratories. Each analyzed fresh cut (FC) tissues and two sites examined sample stability by analyzing the impact of storing slides at -80°C for 1 month prior to spatial profiling. Concordance analysis was performed using the Horn-Morisita Index on raw data comparing paired and unpaired ROIs across each set of slides.

In CPA samples where each pellet was a different tumor type (e.g., NSCLC, melanoma), we observed strong clustering by cell line. While data initially showed varying degrees of clustering by slide, factoring out this variable removed the association of slide, allowing integration of the data across profiling locations without affecting concordance within slides. In tonsil, ROIs with increasing area were profiled. Comparing expression between pairs of samples for a given area, concordance increased with ROI size (R = -0.40, p<6e-06). Finally, we observed little impact of preservation method (FC vs -80°C) in these data.

In this study, we quantify slide-specific variation observed in high-plex RNA profiling by the DSP platform and detail methods for accounting for this variation. We note that many downstream analyses (e.g., differential expression) already model slide effects during the analysis, but modeling it explicitly allows for direct comparison of concordance with other approaches (e.g., clustering, PCA). These methods support the use of multi-institution studies leveraging the GeoMx platform.

Citation Format: Tyler Hether, Tim Howes, David Scoville, Charlie Glaser, Yanyun Li, Rami Vanguri, Neeman Mohibullah, Wan-Jung Chang, Todd Yoder, Minnal Gupta, Kathy Ton, Yan Liang, Ying Huang, Zach Herbert, Jason Reeves, Elizabeth Mittendorf, Simon Lacey, Travis Hollmann, Sarah Warren, Theresa LaVallee. A multi-institution examination of concordance in spatial transcriptomics using the GeoMx Cancer Transcriptome Atlas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 66.

Abstract P1-04-13: Generation and validation of an estrogen receptor signaling (ERS) gene panel that inversely correlates with antigen presentation and T cell infiltration and activity in hormone receptor positive (HR+) breast cancer

Background: Tumor infiltrating lymphocytes (TILs) are observed in low numbers in HR+ breast cancer relative to other subtypes. For T cells (TC) to recognize and respond to a tumor, antigens must be presented on the tumor cell surface via human leukocyte antigen class one (HLA-I) molecules. Hence, the lack of immune infiltration into HR+ tumors could be explained by limited antigen or impaired antigen presentation. We hypothesized that ERS inversely correlates with antigen presentation and T cell infiltration in HR+ tumors. The objective of this study was to comprehensively examine the relationship between ERS, antigen presentation machinery (APM) and TC gene expression in HR+ breast cancer.Methods: Comprehensive gene panels for ERS, APM and TC expression were generated from literature review, GO terms, KEGG pathways, REACTOME, and computationally and manually curated gene lists. Genes expressed in both The Cancer Genome Atlas (TCGA) and Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) were used for subsequent analyses. Tumors were classified into 4 major subtypes (HR+/HER2-, HR+/HER2+, HR-/HER2+, HR-/HER2-) based on estrogen receptor (ER), progesterone receptor and HER2 expression as defined by immunohistochemistry. To statistically refine each gene panel, the genes were hierarchically clustered based on their pairwise Spearman correlation coefficients among HR+/HER2- samples in TCGA (n = 441) and METABRIC (n = 1028). Specifically, clusters were identified by linkage with 2 hallmark genes for each panel: ESR1 and FOXA1 for the ERS panel, HLA-A and NLRC5 for the APM panel, and CD8A and CD8B for the TC panel. Due to overlapping genes in the APM and TC panels, these two panels were combined for subsequent analyses. Final gene panels for ERS and APM/TC were generated from overlapping genes identified in corresponding TCGA and METABRIC clusters. Internal validity of the final gene panels was assessed through pathway enrichment analysis. The panels were then validated through correlation analysis in an independent single institution cohort (HR+ = 25, HER2+ [regardless of HR] = 25, TNBC = 23). Finally, intra and inter-panel correlation analysis results were compared between breast cancer subtypes in both TCGA and METABRIC datasets. Results: Among the 988 genes identified in our manually curated panels, 788 genes were recognized in both TCGA and METABRIC datasets. Statistical refinement resulted in a final 28-gene ERS panel and a final 135-gene combined APM/TC panel. Early and late-estrogen response pathways were enriched in the ERS panel, whereas interferon-gamma response and other innate and acquired immune-related pathways were enriched in the APM/TC panel. Strong inverse correlations between ERS and APM/TC panels were identified in both TCGA and METABRIC datasets. These findings were validated in the single institution cohort where we noted the strength of the correlations varied with the subtype of disease and extent of HR expression. Further analyses in all 4 breast cancer subtypes, in both TCGA and METABRIC datasets, revealed consistent positive correlations within the APM/TC panel across all subtypes. However, positive correlations within the ERS panel corresponded to the subtypes’ dependency on ER pathway, with a strong correlation in HR+ breast cancer and limited correlation in HR- tumors. Conclusions: Using an unbiased data-driven approach, ERS and APM/TC gene panels were generated. Among HR+ tumors, high levels of ERS gene expression significantly correlated with lower levels of APM/TC gene expression providing one potential mechanism for low TC infiltration in HR+ breast cancer. The prognostic and predictive values of these panels are currently being investigated.

Citation Format: Jonathan S Goldberg, Xiaoyong Cui, Kenichi Shimada, Sandra McAllister, Sara Tolaney, Adrienne Waks, Rinath Jeselsohn, Jennifer Guerriero, Judith Agudo, Elizabeth Mittendorf. Generation and validation of an estrogen receptor signaling (ERS) gene panel that inversely correlates with antigen presentation and T cell infiltration and activity in hormone receptor positive (HR+) breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-04-13.

Abstract ES5-2: Optimizing the management of early stage TNBC

The recent approvals of the immunotherapeutic agent pembrolizumab, the antibody-drug conjugate sacituzumab govitecan and the PARP inhibitors olaparib and talazoparib for select patients with metastatic triple negative breast cancer (TNBC) have spurred interest in evaluating these and other novel agents in patients with earlier stage disease. For the last several decades, a standard approach to treating early stage TNBC was to administer neoadjuvant chemotherapy, most often an anthracycline/taxane-based regimen. Pathologic complete response (pCR) rates generally ranged 30-40%. Trials such as CALGB 40603, GeparSixto and BrighTNess demonstrated that the addition of carboplatin to an anthracycline and taxane based chemotherapy could increase the pCR rates (53-58%). At the most recent ESMO conference, the BrighTNess investigators reported that the addition of carboplatin improved event free survival (EFS) after a median follow-up of 4.5 years. For patients not experiencing a pCR, the Create-X trial showed benefit of capecitabine in the adjuvant setting.As of August 2021, there is a new standard for treating early stage TNBC. Specifically, based on the KEYNOTE-522 trial, pembrolizumab, in combination with chemotherapy, is FDA approved for this indication. KEYNOTE-522 enrolled over 1170 stage 2-3 TNBC patients and randomized them to chemotherapy +/- pembrolizumab. The most recent report showed the trial met it’s co-primary endpoints of improved pCR (63% vs 56%) and EFS (84.5% vs 76.8%) after a median follow-up of 39 months. Importantly, the benefit was regardless of the PD-L1 status of the patient’s tumor. With the approval of pembrolizumab comes a number of questions: 1) which patients should receive this regimen which is associated with immune-related toxicities, some of which are lifelong, 2) what is the optimal chemotherapy backbone, 3) is a full year of pembrolizumab required and 4) are there other biomarkers to be explored that may predict response to therapy or the development of toxicity? Other studies either have or are evaluating other targeted agents in the preoperative setting for early stage TNBC. In a small study of 20 BRCA mutation carriers treated preoperatively with single agent talazoparib, investigators reported a pCR rate of 53%. A study looking at sacituzumab monotherapy in the preoperative setting has completed accrual and the results are awaited. These two trials begin to address the question of whether we can identify an “achilles” heel in TNBC and if so, will targeting it improve patient outcomes. Good correlative studies that provide improved understanding of the impact of these therapies on the TNBC microenvironment will help inform the next generation of trials; likely combination therapies.There is also the question of adjuvant therapy, particularly for those that do not experience a pCR with preoperative therapy. As stated above, the CREATE-X trial supports the use of capecitabine in patients with residual disease, however EA1131 demonstrated that outcomes are still poor for this population. More recently, for patients with BRCA-mutated cancers, the OlympiA trial showed benefit to a year of adjuvant olaparib. There is also growing interest in whether patients with residual disease who are at highest risk for recurrence can be identified using technologies looking for cell-free DNA to find those with minimal residual disease. Historically we’ve thought about TNBC for what it’s not – it is not ER, PR or HER2 positive. With multiple studies now showing benefit of specific agents in TNBC, the next several years will provide an opportunity to more extensively dissect triple negative tumors and their. microenvironment. This will allow us to learn what TNBC “is”, and which of likely multiple different therapeutic strategies will be best applied to which patients.

Citation Format: E Mittendorf. Optimizing the management of early stage TNBC [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr ES5-2.

Abstract P5-13-15: High dimensional flow cytometric analysis or the peripheral immune profile and response to HER2-targeted antibody therapy

Background: DAPHNe was a prospective trial designed to assess adherence to de-escalated antibody doublet therapy in the adjuvant setting among HER2+ breast cancer patients experiencing a pathologic complete response (pCR) following neoadjuvant taxol (T), trastuzumab (H) and pertuzumab (P). Peripheral blood mononuclear cells (PBMC), were collected from all patients at baseline and after THP completion. The goal of this study was to determine if a patient’s peripheral blood immune profile at baseline, or the longitudinal change with treatment, could predict response to THP. Methods: Blood samples were subjected to high dimensional (28-30 parameter) flow cytometry with comprehensive T- and NK-cell panels. A fully automated computational analysis strategy was undertaken consisting of unsupervised clustering of the high dimensional data into groups of cells with similar immunophenotypic signatures. Clustering was performed using 2 algorithms: Fingerprint-based clustering (Fluster) and High Throughput Mapper (HiTMapper). Clusters were tested using the Wilcoxon rank-sum test for correlation with the clinical response. Responders were those with pCR (=residual cancer burden [RCB] 0) or RCB 1; non-responders were those with RCB 2/3 disease. P values were adjusted with the Benjamini-Hochberg method to control for FDR. In addition to P values, effect size was evaluated using the nonparametric Cliff’s Delta measure. An effect was determined to be large if the magnitude of Delta was >0.4 which corresponded to one cohort coming ahead 70% of the time. In addition, groups of clusters were evaluated using multivariate statistical modeling or dimensionality reduction to determine if there was an association with pCR. Results: Matched baseline and pre-op PBMC were available to perform the NK panel in 66 patients and the T cell panel in 40. In both groups 70% were responders and 30% were non-responders. No cluster produced by Fluster or HiTMapper differed significantly between responders and non-responders however, in the T cell panel, several clusters had a large effect size (table) suggesting the clusters are good at differentiating some, responders from non-responders. Both algorithms agreed that the median responder has more CD4 naïve and CD8 naïve cells than the median non-responder. While no individual cluster differed significantly between responders and non-responders, cross-validated logistic regression analyses showed that 2 clusters, activated CD4 central memory clusters, and activated CD4 naïve clusters, predicted responder status with AUC of 0.70 and 0.68 respectively. Numerous clusters showed robust and significant longitudinal changes between baseline and pre-op samples. Stratifying longitudinal changes by response status revealed no significant differences between responders and non-responders, however evaluation of effect size suggested a naïve CD4 cluster that increased in non-responders and decreased in responders. The latter could be explained as naïve T cells acquiring a memory phenotype in response to treatment in responders. Conclusion: High dimensional flow cytometry suggested a potential role for monitoring several T cell subsets to predict response in HER2+ patients receiving THP. Additional analyses to include cyTOF evaluation of PBMCs are ongoing to further characterize the peripheral immune profile of these HER2+ patients.

T cell clusters with high effect sizeMajor PhenotypeOther markersMethodp-valueeffect sizeCD4 CM.actCD38, CD226HiTMapper0.351-0.469CD4 Naive.act.2CD38, CD226HiTMAPPER0.4-0.413CD4 Naive.act.4CD226HiTMapper0.351-0.490CD4 Naive.act.5CD38HiTMapper0.351-0.524CD8 Naive 1CD226HiTMapper0.396-0.427CD3 Neg-Fluster0.3190.476CD3 Neg3CD45RA, CD185, CD197Fluster0.3190.476CD3 Neg4CD45RA, Eomes,tBETFluster0.4240.413CD4 Naive-Fluster0.319-0.517CD8 Naive1-Fluster0.319-0.469Unassigned 20 (CD4)CD45RA, CD27-, CD28-Fluster0.364-0.441

Citation Format: Esther R Ogayo, Adrienne Waks, Wade Rogers, Matei Ionita, Kenechukwu Adigwe, Jillian Alberti, Sapana Kadel, Jonni Moore, Tari King, Ian Krop, Sara Tolaney, Eric Winer, Jennifer Guerriero, Elizabeth Mittendorf. High dimensional flow cytometric analysis or the peripheral immune profile and response to HER2-targeted antibody therapy [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-13-15.

Understanding resistance to immune checkpoint inhibitors in advanced breast cancer

INTRODUCTION

The addition of immune checkpoint inhibitors (ICIs) to frontline chemotherapy has improved survival for patients with advanced triple-negative breast cancer (TNBC) expressing programmed death-ligand 1 (PD-L1). Nonetheless, most patients develop resistance, with outcomes remaining poor for this population. Moreover, unsatisfactory activity has been observed with ICIs in PD-L1-negative TNBC and in other breast cancer (BC) subtypes, warranting a deeper understanding of resistance to ICIs in BC.

AREAS COVERED

We discuss the immune landscape of distinct BC subtypes, review the clinical activity of immunotherapy in BC, and highlight strategies under development to overcome resistance to ICIs.

EXPERT OPINION

Activity and resistance to ICIs in BC are strongly related to the intrinsic immunophenotype of the tumor tissue. Several promising biomarkers reflecting the immunological state of BC are emerging, with only PD-L1 expression currently adopted into clinical practice. However, limitations make of PD-L1 a sub-optimal biomarker for patient selection, which require efforts to integrate this marker with other immunological features. Concomitantly, a wide variety of drug combinations designed to overcome immune-resistance are being evaluated, with some encouraging signals observed in early-phase trials. Combination strategies tailored to patient and tumor immunophenotype may allow to overcome resistance and fully exploit the potential of ICIs.

614 Investigating immune mediated mechanisms of PARPi resistance in BRCA1-associated triple negative breast cancer (TNBC)

Background

Poly(ADP-ribose) polymerase inhibitors (PARPi) have improved the outcomes of BRCA-associated breast cancer; however, treatment responses are often not durable. Our preclinical studies demonstrated that PARPi activates the cGAS/STING pathway and recruitment of anti-tumor CD8+ T-cells that are required for tumor clearance [1]. These studies contributed to development of clinical trials testing PARPi plus immune checkpoint blockade (ICB). Unfortunately, early phase trials of PARPi + ICB have not yet suggested efficacy will be superior to PARPi monotherapy. Lack of demonstrated clinical synergy between PARPi + ICB underscores the need to study the tumor microenvironment (TME) during PARPi therapy to identify optimal strategies to enhance T-cell activation. We recently showed that PARPi induces CSF-1R+ suppressive tumor associated macrophages (TAMs) that restrict antitumor immune responses, contributing to PARPi resistance [2]. Removing TAMs with anti-CSF-1R therapy in combination with PARPi significantly enhanced overall survival (OS) compared to PARPi monotherapy in preclinical models [2]. Here, we investigate how modulating TAMs can enhance PARPi + ICB.

Methods

Mice bearing BRCA1-deficient TNBC (K14-Cre;Brca1f/f;p53f/f) tumors were treated for 98 days with PARPi (Talazoparib) ± small molecule inhibitor of CSF-1R (ARRAY-382; CSF-1Ri) ± anti-PD-1 and then followed for survival. Flow cytometry was employed to elucidate changes in the TME after treatment.

Results

PARPi conferred a significant survival advantage over vehicle treated mice (median OS 33 v. 14 days; p=0.0034) and 2/8 PARPi-treated mice experienced complete tumor clearance at day 98. PARPi + CSF-1Ri treated mice (median OS 140 days) remarkably cleared 7/10 tumors by day 98. The addition of anti-PD-1 to PARPi did not enhance OS compared to PARPi monotherapy. The triple combination of anti-PD-1 + PARPi + CSF-1Ri has not yet significantly enhanced the median OS compared to PARPi + CSF-1Ri (ongoing; 168 v. 140 days); nor did it increase clearance of tumor by day 98 (7/10). However, the triple combination led to superior long term tumor clearance. At day 161 the triple combination exhibited 5/10 tumor free mice compared to 2/10 treated with PARPi + CSF-1Ri. To elucidate how CSR-1Ri enhanced PARPi + ICB responses, flow cytometry was performed and revealed increased expression of the co-stimulatory molecule CD80, reduced tissue resident macrophages (CX3CR1+) and lower CSF-1R expression compared to PARPi + ICB.

Conclusions

These data suggest that targeting immunosuppressive macrophages may induce a favorable anti-tumor immune response and enhance responses to PARPi plus ICB. We are currently evaluating the adaptive immune response in this context.

References

Pantelidou, C., et al., PARP inhibitor efficacy depends on CD8+ T cell recruitment via intratumoral STING pathway activation in BRCA-deficient models of triple-negative breast cancer. Cancer Discovery, 2019: p. CD-18-1218.

Mehta, A.K., et al., Targeting immunosuppressive macrophages overcomes PARP inhibitor resistance in BRCA1-associated triple-negative breast cancer. Nat Cancer, 2021. 2(1): p. 66–82.

Abstract PS14-21: Refining loco-regional therapy for inflammatory breast cancer protocol in progress

Background: Inflammatory breast cancer (IBC) is the most aggressive locally advanced breast cancer subtype. It is associated with loco-regional recurrence rates of 12-25%, and neoadjuvant chemotherapy (NAC) followed by modified radical mastectomy and comprehensive chest wall and regional nodal radiotherapy remain the standard of care. As has been demonstrated in non-IBC, achievement of pathologic complete response (pCR) has been shown to be associated with improved loco-regional control, recurrence-free and overall survival. Advances in NAC for IBC have resulted in improved pCR rates in both the breast and the axilla, with overall axillary pCR rates of approximately 30%, reaching as high as 67% in patients with HER2-positive disease receiving HER2-directed therapy. Hypothesis: Sentinel lymph node biopsy (SLNB) may be feasible in IBC patients who experience a good clinical and pathologic response in the axilla to NAC. Primary Objective: To evaluate the sentinel lymph node (SLN) identification rate in stage III IBC patients who experience cN0 status at completion of NAC. Secondary Objective: To assess the incidence of lymphedema following standard local-regional therapy for IBC. Methods and Study procedures: In this feasibility study, 50 patients with cT4dN0-2M0 IBC will be enrolled in order to evaluate 40 patients whose axillary nodal status becomes cN0 upon completion of NAC. All patients will undergo a research breast biopsy and lymphoscintigram pre and post NAC to evaluate lymphatic drainage patterns and patency of breast and axillary lymphatics. Post NAC lymphoscintigraphy will be appropriately timed for pre-operative SLN mapping and all patients will undergo SLNB using dual tracers (Tc99 Sulfur colloid and blue dye) with immediate axillary lymph node dissection (ALND), at the time of mastectomy. The patient-reported Lymphedema Symptom Intensity and Distress Survey (LSIDS-A) will be collected at 6 timepoints. Patients will be followed for 2 years post-surgery for oncologic outcomes. Correlatives: We plan to evaluate genetic and phenotypic heterogeneity in IBC and to assess markers of angiogenesis and lymph-angiogenesis associated with IBC, as well as to explore immunologic aspects of the tumor microenvironment and their association with pCR. Statistics: The identification rate will be calculated as number of patients in whom SLNs were successfully identified over the number of patients with cN0 disease after NAC in whom SLN mapping was attempted. Using a Simon two-stage design (α=.10, β=.10), a SLN identification rate of ≥90% would result in considering this procedure feasible whereas an identification rate of ≤75% (null hypothesis) would lead to the conclusion that it is not feasible. In the first stage, if greater than 18 of 25 patients have SLNs identified, then a total of 40 patients will be enrolled. If fewer than 33 of 40 patients have SLN identified, then the null hypothesis is rejected.

Citation Format: Faina Nakhlis, Meredith Regan, Heather Jacene, Beth Harrison, Jennifer Bellon, Jean Landry, Eren Yeh, Elizabeth Mittendorf, Beth Overmoyer, Tari King. Refining loco-regional therapy for inflammatory breast cancer protocol in progress [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 PS14-21.

Abstract SP097: Local Regional Management Following Neoadjuvant Chemotherapy: Minding the Knowledge Gaps

Neoadjuvant chemotherapy is often used in managing breast cancer patients, particular those with HER2-positive (HER2+) or triple negative disease. Among the known benefits of administering chemotherapy prior to surgery is the opportunity to assess response which informs prognosis. The CTneoBC analysis, which included 12 trials enrolling over 11,950 patients, showed that patients experiencing a pathologic complete response (pCR; ypT0ypN0 or ypT0/isN0) have improved event-free and overall survival with the association between pCR and longterm outcomes being strongest in patients with triple negative breast cancer (TNBC) and in those with HER2+/hormone receptor-negative breast cancer receiving trastuzumab. In triple negative and HER2+ breast cancer, the response to neoadjuvant chemotherapy also informs the need for additional adjuvant therapy. For patients with TNBC and significant residual disease after neoadjuvant chemotherapy, the CREATE-X trial showed benefit for adjuvant xeloda. For patients with HER2+ breast cancer not experiencing a pCR to neoadjuvant chemotherapy plus HER2-targeted therapy, the KATHERINE trial showed a significant improvement in invasive disease-free survival and overall survival in patients receiving adjuvant T-DM1 versus adjuvant trastuzuamb. With respect to considerations for local regional therapy, it is known that neoadjuvant chemotherapy decreases the primary tumor size such that tumors thought to be inoperable become operable and tumors thought to require mastectomy downstage to be eligible for lumpectomy. More recently it has been shown that neoadjuvant chemotherapy can decrease the extent of axillary surgery required. While historically patients with clinically node positive disease at presentation were thought to require axillary lymph node dissection (ALND), the American College of Surgeons Oncology Group Z1071 trial demonstrated that sentinel lymph node biopsy (SLNB) was feasible in those who convert to clinically node negative disease following neoadjuvant chemotherapy. These findings were confirmed in the European SENTINA trial and Canadian SN-FNAC study. All three of these studies suggested that technical aspects of the SLNB procedure were critical to ensure a sufficiently low false negative rate. While these are the “known knowns”, there are many “known unknowns” and evolving data, particularly as it relates to local regional therapy following neoadjuvant chemotherapy. Included among the “known unknowns” are the optimal imaging modality to assess response to neoadjuvant chemotherapy thereby facilitating surgical planning, optimal technique for performing SLNB for those patients converting from clinical N1 to clinical N0 disease after neoadjuvant chemotherapy, the definition of negative margins for a lumpectomy, the role of routine use of immunohistochemistry for cytokeratins in pathologic evaluation of the sentinel lymph nodes, the optimal method for pathologic staging following neoadjuvant chemotherapy, and the role of ALND versus radiation therapy for patients with residual nodal metastases in the sentinel nodes. More recently, it has been questioned whether patients experiencing a complete radiographic response can undergo image guided biopsy in lieu of surgery; yet data from 3 prospective series demonstrate unacceptably high false negative rates with this approach. Given the significant implications of accurately assessing response to therapy and the presence of residual disease, optimizing local regional management is a critical component of the multidisciplinary care of these patients. In this lecture, the available data guiding local regional management after neoadjuvant chemotherapy will be reviewed with attention focused on areas in which there is limited data, therefore knowledge gaps.

Citation Format: E Mittendorf. Local Regional Management Following Neoadjuvant Chemotherapy: Minding the Knowledge Gaps [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 SP097.

Abstract PD12-11: Patient-reported outcomes from the Phase III IMpassion031 trial of neoadjuvant atezolizumab + chemotherapy in early triple-negative breast cancer

Background: In the IMpassion031 study (NCT03197935) of patients (N = 333) with invasive stage II or III early triple-negative breast cancer (eTNBC), neoadjuvant treatment with atezolizumab vs placebo, each combined with nab-paclitaxel followed by doxorubicin + cyclophosphamide, significantly improved pathologic complete response in the intent-to-treat population. Patient-reported outcomes (PROs) were collected to document patient perspectives on overall treatment burden and clinical benefit of atezolizumab + chemotherapy for neoadjuvant treatment of eTNBC. Methods: Patients received either atezolizumab 840 mg or placebo every 2 weeks (q2w) with nab-paclitaxel 125 mg/m2 every week for 12 weeks followed by atezolizumab 840 mg or placebo q2w with doxorubicin 60 mg/m2 + cyclophosphamide 600 mg/m2 q2w for 4 cycles. After surgery, patients in the atezolizumab arm were unblinded and continued to receive atezolizumab 1200 mg every 3 weeks for 11 doses, while patients in the control arm did not receive any study treatment. Patients completed the EORTC Quality of Life Questionnaire Core 30 (QLQ-C30) and single-item GP5 from the Functional Assessment of Cancer Therapy-General (FACT-G) questionnaire at baseline and day 1 of each cycle of neoadjuvant and adjuvant treatment, at end of treatment and during follow-up every 3 months during year 1, every 6 months during years 2-3, and then annually. Mean and mean change from baseline scores (with changes ≥ 10 considered clinically meaningful) in function (role and physical) and global health status/health-related quality of life (GHS/HRQoL) were predefined secondary endpoints. Mean and mean change from baseline scores in disease and treatment-related symptoms, as well as an assessment of overall side-effect bother, were exploratory endpoints. Expected results: The PROs will be compared between the atezolizumab and placebo arms to assess overall treatment burden and the effect of adding atezolizumab to neoadjuvant chemotherapy for the treatment of eTNBC.

Citation Format: Elizabeth Mittendorf, Nadia Harbeck, Hong (Amy) Zhang, Shigehira Saji, Kyung Hae Jung, Sheetal Patel, Shilpen Patel, Anh Nguyen Duc, Mario Liste-Hermoso, Stephen Y Chui, Carlos H Barrios. Patient-reported outcomes from the Phase III IMpassion031 trial of neoadjuvant atezolizumab + chemotherapy in early triple-negative breast cancer [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 PD12-11.

Abstract OT-33-01: Combination ipatasertib and atezolizumab to prevent recurrence in triple negative breast cancer(TNBC): A phase II single arm trial

Background: TNBC patients with residual disease after neoadjuvant chemotherapy (NAC) have high recurrence rates. Targetable mechanisms likely responsible for NAC resistance must therefore be identified to identify new therapeutic options. Alterations in the PI3K/mTOR pathway as well as expression of the immune checkpoint PD-L1 have emerged as potential targets, with significant frequency of alteration in TNBC. Importantly, the AKT inhibitor ipatasertib (ipat) and the anti-PD-L1 antibody atezolizumab (atezo) have demonstrated activity against TNBC. Recent data suggests that the presence of circulating tumor cell-free DNA (cfDNA) following NAC correlates with residual disease and a higher recurrence risk. We have hypothesized that combination therapy with ipat and atezo will target micrometastatic disease, as determined by the presence of cfDNA after NAC, in TNBC patients. Trial design:Open label single-arm phase II study to evaluate combination therapy with ipat and atezo, in TNBC patients with detectable cfDNA after completion of NAC, definitive surgery, and adjuvant radiation and/or chemotherapy. Eligible patients will receive: atezo [840mg IV days 1 and 15 and ipat [400 mg orally daily on days 1-21, followed by one week off] in a 28-day cycle for 6 cycles; cfDNA will be evaluated after 3 and 6 cycles. Biomarkers including PD-L1 expression on tumor cells or infiltrating immune cells in the primary tumor or PD-L1 expression on circulating tumor cells will be assessed. Eligibility criteria:Patients ≥ 18 yrs of age with pathologically confirmed residual invasive TNBC (ER and PR negative defined as <10% of cells expressing ER/PR by local assessment; HER2 negative according to ASCO/CAP guidelines) following NAC with evidence of cfDNA after completion of all local and systemic neoadjuvant and adjuvant therapy. Patients must enroll within 12 months of last therapy (definitive breast surgery, radiation and/or all intended adjuvant therapy). Prior treatment with immunotherapeutic agents is allowed. Specific aims:The primary objective is to evaluate the efficacy of 6 cycles of ipat + atezo in reducing micrometastatic disease (detectable cfDNA) in patients with residual breast and/or axillary disease after NAC and completion of all locoregional and/or systemic adjuvant therapy. Secondary objectives include: evaluating efficacy of ipat + atezo in reducing micrometastatic disease after 3 cycles; determining the recurrence risk after treatment with ipat + atezo; and determining the safety and tolerability of the combination. Correlative objectives include determining whether: 1) pretreatment circulating markers (mutations or copy number changes in PTEN/PI3K/AKT) are associated with response; 2) PD-L1 expression on tumor cells or infiltrating tumor cells in the primary tumor is associated with response; 3) PD-L1 expression on circulating tumor cells has utility as a pharmacodynamic biomarker; and 4) stool microbiome profiles are associated with response and/or survival. As an exploratory objective, patient attitudes and experience surrounding testing for tumor cfDNA and, for those testing positive, participation in a trial targeting cfDNA, will be assessed. Statistical methods:The primary objective is to determine the response rate defined as the proportion of patients with detectable cfDNA who become undetectable. We anticipate that 30% of patients screened will be tumor cfDNA-positive, thus anticipate screening ~ 120 patients to enroll 40. With 40 patients enrolled (assuming a one-sided alpha of 0.05), we will have 80% power to detect a 19.0% (81% positive versus 93% positive) clearance rate using a one-sample binomial exact test. Target Accrual:40 patients Contact:A. DeMichele (angela.demichele@pennmedicine.upenn,edu) Clinicaltrials.gov #: NCT04434040

Citation Format: Elizabeth Mittendorf, Sara Tolaney, Paul Wileyto, Michelle DeMeo, Hope Rugo, Rita Nanda, Ingrid Mayer, Ben Park, Heather MacArthur, Angela DeMichelle. Combination ipatasertib and atezolizumab to prevent recurrence in triple negative breast cancer(TNBC): A phase II single arm trial [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 OT-33-01.

Abstract PS4-05: Prospective evaluation of the gut microbiome and response to neoadjuvant therapy (NAT) in early-stage triple negative breast cancer (TNBC)

Introduction: Emerging data suggest that the gut microbial composition influences responses to chemotherapy and immunotherapy. However, similar data in patients with TNBC receiving NAT remains limited. Thus, we investigated the association between the gut microbial composition in patients with newly-diagnosed, early-stage TNBC and response to NAT in a cohort of patients enrolled in the ARTEMIS trial (NCT02276443). Methods: We performed 16S sequencing on bacterial genomic DNA extracted from pre-NAT 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 128. Associations between abundance and pathologic response to NAT were assessed using the Mann Whitney U Test. A cohort of 32 patients had longitudinal samples collected. Mann-Whitney U Test and Fishers exact were used to compare clinical variables as appropriate between the pCR and non-pCR groups. Results: There was no significant difference in age, race or stage between the pCR and non-pCR groups (Table 1). As expected, the pCR group was enriched for high TIL (p=0.026). There was no difference in alpha-diversity of the gut microbiome between patients with NAT-sensitive (pCR) and NAT-resistant disease (non-pCR) (p=0.5). Relative to patients with NAT-sensitive disease (pCR), the gut microbiome in patients with NAT-resistant disease was enriched for Fusobacterium (p=0.009), Intestinimonas (p=0.01) and Lachnospiraceae (p=0.003) at the genus level; the median abundances between pCR and non-pCR are provided in Table 1. Longitudinal samples collected during NAT demonstrated no substantial impact of NAT on the gut microbiome.

Conclusions: Taken together, these data suggest that response to NAT may be influenced by the gut microbial composition, which remains unaltered during NAT. Research efforts to modulate the gut microbiome should be further explored as a potential therapeutic strategy in TNBC.

Table 1: Median Microbial Abundance and Clinicopathological Variables (N=43)pCR (n=18)Non-pCR (n=25)p- valueMicrobial AbundanceFusobacterium1 x 10-61.02 x 10-50.009Intestinimonas6.4 x 10-54.8 x 10-40.01Lachnospiraceae6.2 x 10-31.0 x 10-20.003Age median, interquartile range (n=44)45 (38-59)53 (46-58)0.61n (%)Race/EthnicityWhite, non-Hispanic11 (61.1)14 (56.0)0.53White, Hispanic4 (22.2)3 (12.0)Black2 (11.1)7 (28.0)Asian1 (5.6)1 (4.0)T categoryT15 (27.8)4 (16.0)0.15T213 (72.2)17 (68.0)T304 (16.0)T400Nodal statusNegative12 (66.7)14 (56.0)0.54Positive6 (33.3)11 (44.0)StageI3 (16.7)3 (12.0)0.91II11 (61.1)15 (60.0)III4 (22.2)7 (28.0)TIL<20%7 (38.9)19 (76.0)0.026>20%11 (61.1)6 (24.0)

Citation Format: Nour Abuhadra, Chia-Chi Chang, Clinton Yam, Ryan Sun, Lei Huo, Jason White, Elizabeth E Ravenberg, Jennifer Litton, Bora Lim, Naoto T Ueno, Banu Arun, Debu Tripathy, Senthil Damodaran, Rashmi Murthy, Vicente Valero, Gabriel Hortobagyi, Nuhad Ibrahim, Alastair Thompson, Elizabeth Mittendorf, Stacy Moulder, Robert Jenq. Prospective evaluation of the gut microbiome and response to neoadjuvant therapy (NAT) in early-stage triple negative breast cancer (TNBC) [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 PS4-05.

Utility of the 21-Gene Recurrence Score in Node-Positive Breast Cancer

The 21-gene Recurrence Score (RS) assay has been validated as both a prognostic and predictive tool in node-negative (pN0), estrogen receptor-positive (ER+), HER2-negative (HER2-) breast cancer. A large body of evidence supports the clinical utility of the RS in the node positive (pN+) population as well. Retrospective analyses of archived tissue from multiple clinical trials have found the RS to be prognostic in both endocrine therapy (ET)-treated and chemotherapy-treated patient with pN+ disease. Distribution of RS results in pN+ patients have also been consistent with those of pN0 populations. Data from the SWOG 8814 trial and large population-based registries further support the prognostic and potential predictive value of the RS. Specifically, patients with 1 to 3 positive nodes and RS less than 18 derived negligible benefit from adjuvant chemotherapy in these studies. In the prospective West German Study Group PlanB and ADAPT trials, pN+ patients with RS less than 11 and RS 25 or less, respectively, who were treated with ET alone experienced excellent outcomes. Finally, 5-year results of the RxPONDER clinical trial randomizing patients with 1 to 3 positive nodes and RS 25 or less to ET alone vs ET plus chemotherapy confirmed an absence of chemotherapy benefit in postmenopausal patients. Clinical practice guidelines support use of the RS in the pN+, ER+/HER2- population, and many institutions have adopted the RS to guide clinical decisionmaking, resulting in a net reduction of adjuvant chemotherapy use. This review highlights the existing data supporting the prognostic and predictive ability of the RS in pN+ disease, current practice patterns related to RS use in this population, and emerging applications.

Optimizing Radiation Therapy to Boost Systemic Immune Responses in Breast Cancer: A Critical Review for Breast Radiation Oncologists

Immunotherapy using immune checkpoint blockade has revolutionized the treatment of many types of cancer. Radiation therapy (RT)-particularly when delivered at high doses using newer techniques-may be capable of generating systemic antitumor effects when combined with immunotherapy in breast cancer. These systemic effects might be due to the local immune-priming effects of RT resulting in the expansion and circulation of effector immune cells to distant sites. Although this concept merits further exploration, several challenges need to be overcome. One is an understanding of how the heterogeneity of breast cancers may relate to tumor immunogenicity. Another concerns the need to develop knowledge and expertise in delivery, sequencing, and timing of RT with immunotherapy. Clinical trials addressing these issues are under way. We here review and discuss the particular opportunities and issues regarding this topic, including the design of informative clinical and translational studies.

Abstract A16: Metformin is a potential nontoxic adjuvant to enhance the efficacy of non-PDL1/PD-1 targeting immune therapies

Investigations into various immunotherapies combined with conventional anticancer drugs are ongoing to increase therapeutic efficacy. However, combination therapy generally increases the risk of side effects. To achieve high efficacy with minimal side effects, nontoxic adjuvants should be identified and appropriate combinations should be designed based on the functional mechanism. In this regard, metformin can be an attractive candidate for immunotherapeutic adjuvants. Metformin is a widely used oral medication for type 2 diabetes (T2D) and has been recognized as a safe and well-tolerated drug through several decades of clinical experience. Interestingly, metformin also exhibits antitumor effects as several case-control studies for T2D patients indicated that metformin reduces the incidence of various cancer types. However, the functions and the detailed mechanism of metformin related to cancer immunity are not fully understood. In this study, we investigated the antitumor effects of metformin in relation to cancer immunity in the tumor microenvironment. Our data showed that AMPK activated by metformin decreases the expression of PD-L1 in the cancer cells, blocking PD-L1’s ability to aid cancer cells in escaping immune surveillance. This is caused by the mechanism in which phosphorylation of PD-L1 at S195 induces an abnormal glycan structure that leads to endoplasmic reticulum-associated degradation. In addition, we have obtained human breast tumor tissues from a previous clinical trial investigating metformin as treatment for breast cancer patients. The data from human tumor tissues also provided strong support to our current conclusion, namely AMPK activated by metformin reduces the level of PD-L1. On the basis of these results, we validated the possibility of metformin as an adjuvant to boost the efficacy of previous immunotherapy without toxicity. Our findings suggest that metformin has strong potential to be used as an adjuvant for immunotherapy. Metformin is expected to have synergistic effect with various non-PDL1/PD-1 targeting immune therapies without additional toxicity.

Citation Format: Jong-Ho Cha, Wen-Hao Yang, Weiya Xia, Yongkun Wei, Li-Chuan Chan, Seung-Oe Lim, Chia-Wei Li, Jennifer Hsu, Hung-Ling Wang, Chu-Wei Kuo, Wei-Chao Chang, Sirwan Hadad, Colin Purdie, Aaron McCoy, Jennifer Litton, Elizabeth Mittendorf, Stacy Moulder, William Symmans, Alastair M Thompson, Helen Piwnica-Worms, Chung-Hsuan Chen, Kay-Hooi Khoo, Mien-Chie Hung. Metformin is a potential nontoxic adjuvant to enhance the efficacy of non-PDL1/PD-1 targeting immune therapies [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr A16.

Abstract P2-16-09: Residual cancer burden in patients with early stage triple negative breast cancer who progress on anthracycline-based neoadjuvant chemotherapy in an ongoing clinical trial (ARTEMIS)

BACKGROUND: Current treatment for early stage triple negative breast cancer (TNBC) includes neoadjuvant systemic chemotherapy (NAST), which is used to assess disease biology and the need for adjuvant treatment in case of residual disease at the time of surgery, also known as residual cancer burden (RCB). Patients with TNBC who experience RCB-0 (pathologic complete response [pCR]) or RCB-I after NAST have an excellent prognosis whereas patients with significant residual disease (RCB-II or RCB-III) are at a high risk of relapse. Standard NAST for TNBC achieves pCR in 30-50% of cases. NAST typically consists of anthracycline-based chemotherapy followed or preceded by a taxane +/- carboplatin. Disease progression (PD) is uncommon in TNBC patients receiving NAST and little is known regarding outcomes in patients who have PD during the initial phase of NAST. METHODS: Total 316 TNBC patients were evaluated from two prospectively accrued clinical trials of NAST (NCT02276443 and NCT01334021). The ARTEMIS trial (NCT02276443) aims to improve pCR rates by adding targeted therapy to chemotherapy as the second phase of NAST for those patients who do not experience at least a 70% volumetric reduction after 4 cycles of doxorubicin/cyclophosphamide (AC). Unique histopathologic features including % stromal tumor-infiltrating lymphocytes (sTIL), presence of mesenchymal histology (high vimentin expression by IHC), and androgen receptor expression are used to guide second phase therapy. RESULTS: 31 TNBC patients had PD while receiving AC as the first phase of NAST (10%; 95% CI= 6.69-13.31%). 9 of 31 patients proceeded to standard chemotherapy and all had RCB II/III disease. 22 of 31 patients were enrolled to targeted therapy trials. 6 were treated with the EGFR inhibitor panitumumab + carboplatin/paclitaxel, 9 with atezolizumab + nab-paclitaxel, and 7 with everolimus, bevacizumab, and liposomal doxorubicin (DAE). Of these 22 patients, 3 (13.6%) had pCR/RCB-0, 1 (4.5%) RCB-I and 18 (81.8%) had RCB II/III. All 4 patients who experienced RCB-0/I had T2N0 disease at diagnosis. 2 had sTIL < 5% and 2 patients had 70% sTIL. CONCLUSION: PD is uncommon while receiving NAST. Patients with TNBC and progression on initial NAST with AC are unlikely to achieve pCR or RCB-I status despite subsequent standard chemotherapy. Combination chemotherapy with targeted therapy on clinical trial resulted in a numerically higher rate of pCR+RCB-I (18%) as salvage therapy, but this was not statistically significant and requires confirmation in larger trials.

Citation Format: Haven Garber, Gaiane Rauch, Beatriz Adrada, Rosalind Candelaria, Elizabeth Mittendorf, Alastair Thompson, Jennifer Litton, Senthil Damodaran, Bora Lim, Banu Arun, Naoto Ueno, Vicente Valero, Nuhad Ibrahim, Rashmi Murthy, Debu Tripathy, Helen Piwnica-Worms, Fraser Symmans, Lei Huo, Stacy Moulder. Residual cancer burden in patients with early stage triple negative breast cancer who progress on anthracycline-based neoadjuvant chemotherapy in an ongoing clinical trial (ARTEMIS) [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 P2-16-09.

Abstract P2-16-08: Longitudinal response and selection under neoadjuvant systemic therapy (NAST) in triple-negative breast cancer (TNBC): Profiling results from a randomized, TNBC enrolling trial to confirm molecular profiling improves survival (ARTEMIS; NCT02276443)

Background: The heterogeneity of TNBC results in a spectrum of responses to NAST: 30-40% of patients (pts) have pathologic complete response (pCR) with excellent prognosis. Several methods have been used to measure and evaluate residual disease, including ultrasound, MRI scans, histo-pathology and transcriptional profiling (Seth, ASCO 2019). In addition, we hypothesize that integrative understanding of sub-clonal selection and changes in molecular pathways would lead to better stratification as a biomarker for chemotherapy, and subsequent targeted therapy trials. Methods: Pts with stage I-III TNBC began a planned 4 cycles of Adriamycin-based chemo (AC). Biopsies were performed pre (mandatory) and post (optional) AC. Volumetric change by ultrasound (VUS) at completion of AC (or progression) was calculated. Pts with sensitive disease received subsequent taxane-based (T) therapy. Pts with insensitive disease were offered phase II trials. Pathologic response was assessed at surgical resection in 55 pts. Matched samples, pre and post AC (N = 55 pts) underwent transcriptomic and genomic profiling. Samples were classified into six previously identified ARTEMIS subtypes of TNBC (ART-Type) and immune deconvolution and estimation was performed using RNA-Seq profiles. Somatic mutations and copy-number changes were evaluated using, Mutect, FACETS, and PyClone. Results: Predominately, tumors reacted to AC in 4 different patterns with variation in immune and EMT related pathways. Enrichment of EMT (Group 4) was associated with poor prognosis and higher RCB (10.3% vs 42% pCR rates, p<0.05). The global changes in transcription led to ART-Type switching in all subtypes (44% of pts), except LAR subtype. MYC amplification was more prevalent (40%) in Group 4, associated with higher EMT and poor prognosis than other groups (28%). Phylogenetic evaluation of selection revealed, sub-clonal selection in 22% of evaluable cases with pre and post biopsies. Conclusions: Molecular profiling of longitudinal TNBC samples reveals distinct response patterns in tumors and their micro-environments upon treatment with AC. Integrative analysis of genomic and transcriptomic changes can lead to better stratification of response to NAST. These patterns were indicative of pathologic response in this cohort; however, they require validation in a separate cohort.

Citation Format: Sahil Seth, Lei Huo, Suhas Vasaikar, Gaiane Rauch, Bora Lim, Jason White, Beatriz Adrada, Helen Piwnica-Worms, Naoto T Ueno, Alastair Mark Thompson, Elizabeth Mittendorf, Debashish Tripathy, Jennifer Keating Litton, William Fraser Symmans, Giulio Draetta, Andrew Futreal, Jeffrey Chang, Stacy Moulder. Longitudinal response and selection under neoadjuvant systemic therapy (NAST) in triple-negative breast cancer (TNBC): Profiling results from a randomized, TNBC enrolling trial to confirm molecular profiling improves survival (ARTEMIS; NCT02276443) [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 P2-16-08.

Abstract MS1-1: Immunotherapy in breast cancer: enhancing response to checkpoint blockade

Historically, breast tumors have been categorized as non-immunogenic in part due to a paucity of tumor infiltrating lymphocytes (TIL) when compared to other histologies. Multiple studies have now demonstrated an endogenous immune response against breast cancer with tumors having TIL present in the tumor and surrounding stroma. The extent of TIL infiltrate is dictated by the subtype of disease being highest in triple negative breast cancer (TNBC) and lowest in hormone receptor positive, HER2 negative (HR+/HER2-) disease. Recent studies have shown that immunotherapy, in the form of immune checkpoint blockade, can be effective in treating breast cancer patients. Specifically, the IMpassion 130 trial, a phase III study that enrolled over 900 patients with metastatic TNBC and randomized them to the immune checkpoint blockade agent atezolizumab plus nab-paclitaxel versus placebo plus nab-paclitaxel, demonstrated benefit to the addition of immunotherapy with respect to progression free survival as well as overall survival; a difference that was greater in patients with PD-L1 positive disease. Based on these data, the combination of atezolizumab plus nab-paclitaxel was approved for use in patients with PD-L1+ metastatic TNBC. More recently, data from a large phase III trial evaluating the use of the immune checkpoint blockade agent pembrolizumab in the neoadjuvant setting for TNBC patients showed a significant improvement in the rates of pathologic complete response. Based in part on these successes, there is significant enthusiasm for using immunotherapy to treat breast cancer patients. It must be recognized however, that a minority of patients respond. Additional work must therefore be done to expand the number of patients with TNBC who respond as well as to identify strategies for successfully employing immunotherapy for HER2+ and HR+ positive breast cancer. Development of these strategies requires understanding of the cancer immunity cycle and how it can be altered to enhance endogenous immune responses to breast cancer as well as improved understanding of the immune aspects of the tumor microenvironment and how standard of care therapies alter that microenvironment. As an example, there is emerging data showing that PARP inhibition leads to cytoplasmic DNA which activates the STING pathway leading to increased expression of release of type 1 interferons, increased MHC expression and antigen presentation and increased infiltration of effector T cells. Ongoing trials are therefore evaluating those agents in combination with immunotherapy. Our lab has shown that PARP inhibition further modifies the tumor microenvironment suggesting additional therapeutic targets. In addition, there is mounting evidence regarding potential mechanisms behind why some subtypes of breast cancer mount a robust immune response while others remain immunologically “cold”. Differences in antigen processing and presentation likely contribute and understanding how HR+ tumors “hide” from immune recognition could contribute to developing strategies to make these tumors susceptible to immunotherapy. Finally, our group has recently published data demonstrating a difference in susceptibility to immune checkpoint blockade based on age suggesting that a patient’s systemic immune status could predict therapeutic response and potentially be manipulated to enhance that response.

Citation Format: E Mittendorf. Immunotherapy in breast cancer: enhancing response to checkpoint blockade [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 MS1-1.

Abstract P5-02-02: Artificial intelligence powered predictive analysis of atypical ductal hyperplasia from digitized pathology images

Background: Approximately 15-25% of patients with atypical ductal hyperplasia (ADH) diagnosed on breast core needle biopsy (CNB) are upgraded to ductal carcinoma in situ (DCIS) or invasive carcinoma (IC) on surgical excision. The reproducible identification of patients with ADH on CNB who are more likely to have upgrades at excision remains elusive. We hypothesized that a machine learning approach could be utilized to train models to recognize ADH on digitized pathology images and to identify cases of ADH more likely to be upgraded to DCIS or IC at excision. The purpose of this study was to determine the accuracy of the machine learning approach to identify ADH.

Methods: 726 digitized images of CNB slides derived from 306 cases with a diagnosis of ADH between 11/2004-3/2018 were included in this study. Independent histologic review by two breast pathologists identified slides with and without ADH from each case. 39 board certified pathologists with experience in evaluation of breast biopsies were employed for tissue region annotation on the PathAI research platform (not intended for diagnostic purposes), yielding 14,118 tissue region annotations. Region annotations included ADH, ADH stroma, flat epithelial atypia (FEA), lobular neoplasia (LN), calcifications (Ca), columnar cell change/hyperplasia, sclerosing adenosis, papilloma, normal terminal duct lobular units and other non-atypical breast tissue regions. These annotations were used to train a convolutional neural network (CNN) with 35 layers and approximately 9 million parameters to identify ADH. The data were split into training and testing sets, representing 61.1% and 38.9% of the data respectively. The distribution of cases, images with ADH and cases with upgrade were balanced between the training and testing sets.

Results: CNB specimens were assigned labels of “ADH” or “No ADH” based on histologic assessment. AI models were able to predict the diagnosis of ADH with 85% sensitivity (144 of 168 images within the test set) and 69% specificity (78 of 113 images within the test set). The slide-level area under the receiver operator curve (ROC) for this model was 0.84.

Conclusions: A deep learning-based classifier showed strong performance for the identification of ADH from whole slide images of H&E stained breast CNBs. With further development, this approach may improve the reproducibility and standardization of the diagnosis of ADH. Future analyses will focus on determining if morphologic features of ADH extracted by the deep learning system can be used to predict upgrade to DCIS and IC. This approach may help stratify patients with ADH on CNB into those who require surgical excision and those who can be followed with active surveillance.

Citation Format: Jennifer K. Kerner, Allison Cleary, Suyog Jain, Harsha Pokkalla, Benjamin Glass, Sam Grossmith, Maya Harary, Elizabeth Mittendorf, Andrew H. Beck, Aditya Khosla, Stuart J. Schnitt, Ilan Wapinski, Tari King. Artificial intelligence powered predictive analysis of atypical ductal hyperplasia from digitized pathology images [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 P5-02-02.

Abstract OT1-08-08: CONTESSA TRIO: A multinational, multicenter, phase 2 study of tesetaxel plus 3 different PD-(L)1 inhibitors in patients with metastatic triple-negative breast cancer (TNBC) and tesetaxel monotherapy in elderly patients with HER2- metastatic breast cancer (MBC)

Background: Chemotherapy treatments with robust efficacy that preserve quality of life are needed. Tesetaxel is a novel, oral taxane that has potential advantages over currently available taxanes, including: oral administration with a low pill burden and once every 3 week (Q3W) dosing; no observed hypersensitivity reactions; preclinical evidence of central nervous system (CNS) penetration; and improved activity against chemotherapy-resistant tumors. More than 600 patients have been treated with tesetaxel in clinical studies. Tesetaxel had robust monotherapy activity in a Phase 2 study in 38 patients with HER2-, HR+ MBC, with a confirmed objective response rate (ORR) per RECIST 1.1 of 45%. CONTESSA TRIO investigates tesetaxel plus 3 different PD-(L)1 inhibitors in patients with TNBC and tesetaxel monotherapy in elderly patients with HER2- MBC.

Trial design: CONTESSA TRIO is a 2-cohort, multinational, multicenter, Phase 2 study.

In Cohort 1, 90 patients (with potential expansion to up to 150 patients) with metastatic TNBC who have not received prior chemotherapy for advanced disease will be randomized 1:1:1 to receive tesetaxel at 27 mg/m2 Q3W plus either: (1) nivolumab at 360 mg Q3W; (2) pembrolizumab at 200 mg Q3W; or (3) atezolizumab at 1,200 mg Q3W. Nivolumab and pembrolizumab (PD-1 inhibitors) and atezolizumab (a PD-L1 inhibitor) are approved for the treatment of multiple types of cancer; atezolizumab, in combination with nab-paclitaxel, was recently approved in the U.S. for the treatment of metastatic TNBC. The dual primary endpoints for Cohort 1 are ORR and progression-free survival (PFS). A sample size of 30 patients in each PD-(L)1 inhibitor treatment group has approximately 70% power to detect an ORR difference of 35% or greater between the treatment group with the highest ORR and the treatment group with the lowest ORR. An increase in the sample size to 50 patients in each treatment group will increase the power to approximately 85%. Secondary endpoints include duration of response (DoR) and overall survival (OS). Efficacy results for each of the 3 PD-(L)1 inhibitor combinations will be assessed for correlation with the results of each of the 3 approved PD-L1 diagnostic assays. CONTESSA TRIO is the first randomized clinical study to compare 3 approved PD-(L)1 inhibitors.

In Cohort 2, 40 elderly patients (with potential expansion to up to 60 patients) with HER2- MBC who have not received prior chemotherapy for advanced disease will receive tesetaxel monotherapy at 27 mg/m2 Q3W. The primary endpoint for Cohort 2 is ORR. A sample size of 40 will allow the ORR to be estimated with a maximum standard error of < 8%. An increase in the sample size to 60 patients will decrease the maximum standard error to < 6.5%. Secondary endpoints include PFS, DoR and OS.

Patients with CNS metastases are eligible for both cohorts. The Study was initiated in March 2019. For further information on this trial, email joconnell@odonate.com or visit clinicaltrials.gov (NCT03952325).

Citation Format: Sara Tolaney, Joanne Blum, Igor Bondarenko, Arlene Chan, Noshir DaCosta, Yin-Hsun Feng, Yann Izarzugaza, Sung-Bae Kim, Mei-Ching Liu, Maria Eva Peréz Lopéz, Mafalda Oliveira, Samuel Guan Wei Ow, Michel Pavic, Hope Rugo, Lee Schwartzberg, Agostina Stradella, Stew Kroll, Joseph O'Connell, Thomas Wei, Elizabeth Mittendorf. CONTESSA TRIO: A multinational, multicenter, phase 2 study of tesetaxel plus 3 different PD-(L)1 inhibitors in patients with metastatic triple-negative breast cancer (TNBC) and tesetaxel monotherapy in elderly patients with HER2- metastatic breast cancer (MBC) [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 OT1-08-08.

Abstract P1-10-20: Serial TILs: Evaluating the role of mid-treatment tumor infiltrating lymphocytes (TIL) in predicting pathologic complete response (pCR) in early-stage triple negative breast cancer (TNBC)

Introduction High levels of TIL at baseline are associated with higher pCR rates and better overall survival in TNBC. Recent studies have also indicated that higher TIL in post-NACT residual disease in TNBC are an important independent predictor of improved survival. We evaluated the role of mid-treatment (post-AC; Adriamycin/Cyclophosphamide) TIL in predicting pCR rates in early-stage TNBC. Methods Of 242 patients with stage I-III TNBC enrolled in the ARTEMIS trial (NCT02276443), 156 patients had pre-AC TIL and pCR status available for this analysis. Both pre-and post-AC TIL counts were available in 29 patients. Post-AC TIL counts for the remaining patients were imputed using linear regression with age, race, stage III, vimentin >50% and post-AC tumor volume reduction. Using these imputed TIL counts we evaluated the association of post-AC TIL with pCR. We also evaluated the change in TIL before and after treatment with AC. Results At baseline the median TIL count was 10% (n=156). In the post-AC samples, the median TIL count was 5%. Using imputed TIL counts, we did not conclude that post-AC TIL was associated with pCR (p= 0.28). Using a cut-point of 15% TIL, our analysis showed that baseline TIL is more strongly correlated with pCR than post-AC TIL (Table 1). In our univariable logistic regression, both baseline TIL and the difference in TIL pre-and post- treatment were significantly associated with pCR (p= 0.0015 and p=0.0068, respectively), however in the multivariable analysis only baseline TIL was significant. Our analysis did show that a decrease in TIL from pre- to post-treatment was significantly associated with pCR (p=0.022). However, this measure was not significant in our logistic regression model when pre-TIL was also included. Conclusion Higher pre-treatment TIL correlated more strongly with pCR rate when compared to post-AC TIL. Pre-treatment high TIL was associated with pCR regardless of changes in TIL pre and post treatment.

Table 1. Changes in TIL before and after treatmentBaseline TILPost-AC TILN#pCR (%)LowLow6217 (27%)LowHigh4012 (30%)HighLow2513 (52%)HighHigh2916 (55%)TIL; Low: <15, High >15

Citation Format: Nour Abuhadra, Kenneth Hess, Jennifer Litton, Gaiane Rauch, Alastair Thompson, Bora Lim, Beatriz Adrada, Elizabeth Mittendorf, Senthil Damodaran, Rosalind Candelaria, Banu Arun, Wei Tse Yang, Naoto Ueno, Lumarie Santiago, Rashmi Murthy, Nuhad Ibrahim, Sahin Aysegul, William Symmans, Lei Huo, Stacy Moulder. Serial TILs: Evaluating the role of mid-treatment tumor infiltrating lymphocytes (TIL) in predicting pathologic complete response (pCR) in early-stage triple negative breast cancer (TNBC) [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 P1-10-20.

Incorporating Patient-Reported Outcome Measures into Breast Surgical Oncology: Advancing Toward Value-Based Care

Value in health care is defined as the health outcome achieved per unit of cost. For health care systems, improving value means achieving better outcomes at lower costs. Improving outcomes, including patient-reported outcomes (PROs), as well as more established metrics such as mortality and complication rates, ensures high-quality care. This is particularly true in breast cancer surgery, where survival and recurrence rates are comparable across different surgical approaches. Outcomes reflecting survivorship quality may therefore better inform decision making regarding surgical approaches. PROs can be assessed using validated instruments known as patient-reported outcome measures (PROMs). They are obtained directly from patients reflecting their health-related quality of life (HRQOL). Ongoing initiatives strive to define PROMs that accurately reflect HRQOL and demonstrate value, with the goal of establishing benchmarks for quality of care. Clinicians caring for patients with breast cancer are well positioned to be involved in defining meaningful measures of value-based breast cancer care. This article reviews value-based breast cancer care in the context of locoregional therapy, with attention paid to the work done by the International Consortium of Health Outcome Measures in which a "standard set" of value-based patient-centered outcomes for breast cancer for international use is defined. In addition, an overview is provided of relevant PROMs and previously reported scores. Recommendations and future challenges for implementation of routine collection of PROs are also discussed. IMPLICATIONS FOR PRACTICE: Opportunity exists to act as early adopters of the routine collection of longitudinal patient-reported outcome data for breast cancer, allowing transition of current care to value-based cancer care.

Outcomes of Curative-Intent Treatment for Patients With Breast Cancer Presenting With Sternal or Mediastinal Involvement

PURPOSE

Optimal treatment of patients diagnosed with de novo metastatic breast cancer limited to the mediastinum or sternum has never been delineated. Herein, we sought to determine the efficacy of multimodality treatment, including metastasis-directed radiation therapy, in curing patients with this presentation.

METHODS AND MATERIALS

This is a single-institution retrospective cohort study of patients with de novo metastatic breast cancer treated from 2005 to 2014, with a 50-month median follow-up for the primary cohort. The primary patient cohort had metastasis limited to the mediastinum/sternum treated with curative intent (n = 35). We also included a cohort of patients with stage IIIC disease treated with curative intent (n = 244). Additional groups included a mediastinal/sternal palliative cohort (treatment did not include metastasis-directed radiation therapy; n = 14) and all other patients with de novo stage IV disease (palliative cohort; n = 1185). The primary study outcomes included locoregional recurrence-free survival (LRRFS), recurrence-free survival (RFS), and overall survival (OS), which were calculated using the Kaplan-Meier method. Cox multivariable models compared survival outcomes across treatment cohorts adjusted for molecular subtype, age, and race.

RESULTS

For the mediastinal/sternal curative-intent cohort, 5-year LRRFS was 85%, RFS was 52%, and OS was 63%. After adjustment, there was no statistically significant difference in LRRFS (hazard ratio [HR], 0.39; 95% confidence interval [CI], 0.13-1.13; P = .08), RFS (HR, 0.87; 95% CI 0.50-1.49; P = .61), or OS (HR, 0.79; 95% CI 0.44-1.43; P = .44) between the stage IIIC cohort and the mediastinal/sternal curative-intent cohort (referent). In contrast, RFS was worse for the mediastinal/sternal palliative cohort (HR, 2.29; 95% CI 1.05-5.00; P = .04). OS was worst for the de novo stage IV palliative cohort (HR, 2.61; 95% CI 1.50-4.53; P < .001).

CONCLUSIONS

For select patients presenting with breast cancer metastatic to the sternum and/or mediastinum, curative-intent treatment with chemotherapy, surgery, and radiation yields outcomes similar to those of stage IIIC disease and superior to de novo stage IV breast cancer treated with palliative intent.

Abstract P3-01-01: Circulating tumor cells (CTCs) after neoadjuvant chemotherapy for triple negative breast cancer (TNBC)

Background: ARTEMIS (A Randomized, TNBC Enrolling trial to confirm Molecular profiling Improves Survival) is a randomized trial to determine if precision guided neoadjuvant chemotherapy (NAC) impacts rates of pathologic complete response in the breast and axillary nodes (pCR). We hypothesized that CTCs in peripheral blood after completion of NAC would provide prognostic information beyond pCR alone in TNBC patients.

Methods: Blood was assessed for CTCs after NAC as part of two IRB approved studies, ARTEMIS (2014 – 0185/PA15-1050), and LAB04-0698. CTCs were identified using the Cell Search® System (Menarini Silicon Biosystems). Samples with one or more cells, also having morphologic criteria for malignancy, were deemed CTC positive. Log-rank test and Cox regression analysis were applied to evaluate associations between CTC positive, pCR, and overall survival.

Results: pCR was achieved in 24/68 (35%) patients with TNBC. Twenty four patients (35%) were CTC positive. Three year overall survival was evaluated in 4 groups of patients: pCR and no CTCs (n=20), pCR and CTC positive (n=4), non-pCR and no CTCs (n=24) and non-pCR and CTC positive (n=20). Three year overall survival was higher in the pCR and no CTCs cohort (100%), compared to pCR and CTC positive (50%), non-pCR and no CTCs (83%), non-pCR and CTC positive (19%); log rank p&lt;0.0001. In the non-pCR and CTC positive patient cohorts, the presence of CTCs was associated with significant risk of death at 3 years [hazard ratio of 12.3 (95% CI 3.4-454, p=0.00002)], whereas a favorable, but non-significant trend was noted for pCR [hazard ratio of 0.2 (95% CI 0.0, 1.4, p=0.11)].

Conclusion: The identification of CTCs after NAC has prognostic significance beyond that of pCR, and should be considered in evaluation of patients for clinical trials of adjuvant therapies.

Citation Format: Lucci A, Hall C, Hess K, Ravenberg E, Clayborn A, Mittendorf E, Rauch G, Candelaria R, Moulder S, Thompson A. Circulating tumor cells (CTCs) after neoadjuvant chemotherapy for triple negative breast cancer (TNBC) [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-01-01.

Epidemiology, Biology, Treatment, and Prevention of Ductal Carcinoma In Situ (DCIS)

Ductal carcinoma in situ (DCIS) is a highly heterogeneous disease. It presents in a variety of ways and may or may not progress to invasive cancer, which poses challenges for both diagnosis and treatment. On May 15, 2017, the Dana-Farber/Harvard Cancer Center hosted a retreat for over 80 breast specialists including medical oncologists, surgical oncologists, radiation oncologists, radiologists, pathologists, physician assistants, nurses, nurse practitioners, researchers, and patient advocates to discuss the state of the science, treatment challenges, and key questions relating to DCIS. Speakers and attendees were encouraged to explore opportunities for future collaboration and research to improve our understanding and clinical management of this disease. Participants were from Dana-Farber Cancer Institute, Brigham and Women's Hospital, Massachusetts General Hospital, Beth Israel Deaconess Medical Center, Duke University Medical Center, and MD Anderson Cancer Center. The discussion focused on three main themes: epidemiology, detection, and pathology; state of the science including the biology of DCIS and potential novel treatment approaches; and risk perceptions, communication, and decision-making. Here we summarize the proceedings from this event.

Abstract P3-08-04: Withdrawn

This abstract was withdrawn by the authors.

Abstract P6-09-06: Updating the AJCC TNM staging system a summary of changes

This abstract was withdrawn by the authors.

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

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

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

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

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

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

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

Abstract P2-01-11: SentimagIC: A non-inferiority trial comparing super paramagnetic iron oxide vs. Tc99 and blue dye in the detection of axillary sentinel nodes in patients with early stage breast cancer

Background: Sentinel lymph node biopsy (SLNB), performed using radioisotope tracer with or without blue dye, is a highly accurate method for staging the axilla in early breast cancer. A radioisotope tracer with or without blue dye is the most commonly used technique for SLNB. Superparamagnetic iron oxide mapping agents detected by a handheld magnetic probe have been explored to overcome the disadvantages of the standard technique which include the short half-life, availability, handling and disposal issues for radioisotope, and the risk of allergic reactions to blue dye. Iron oxide mapping agents have been shown to be non-inferior to the standard technique in European studies. The SentimagIC trial was designed to establish the non-inferiority of a new formulation of the magnetic tracer, SiennaXP, to the combination of radioisotope and blue dye and was required to support a US regulatory submission.

Methods: Between January and December 2015, 160 patients with clinically node negative early stage breast cancer were recruited from six centers in the United States. Subjects received radioisotope injection then an intraoperative subareolar injection of SiennaXP and isosulfan blue dye prior to SLNB being performed. The sentinel node identification rate was compared between SiennaXP and the standard technique to evaluate concordance and non-inferiority.

Results: 147 procedures were completed in 147 subjects. A total of 369 histologically confirmed nodes were excised. The nodal detection rate was 94.3% (348/369) with SiennaXP and 93.5% (345/369) with the standard technique (difference 0.8%, 95% binomial confidence interval lower bound -2.1%). The per-subject detection rate was 99.3% (145/146) with SiennaXP and 98.6% (144/146) with the standard technique (one subject excluded due to not contributing any analyzable nodes). There were 22 subjects with positive SLNs, of whom 21 (95.4%) were detected by both SiennaXP and the standard tracers. In one subject, a positive node was not identified by any tracer, but was removed as clinically suspicious. The number of nodes excised per subject was 2.4 for both SiennaXP and for the standard combined technique.

Conclusion: This study showed SiennaXP is non-inferior to the standard dual technique of radioisotope and blue dye for axillary sentinel lymph node detection in early stage breast cancer and this provides a potential alternative to radioisotope and blue dye.

Citation Format: Alvarado M, Bold R, Gittleman M, Beitsch P, Blair S, Harmer Q, Kivilaid K, Teshome M, Thompson A, Mittendorf E, Hunt K. SentimagIC: A non-inferiority trial comparing super paramagnetic iron oxide vs. Tc99 and blue dye in the detection of axillary sentinel nodes in patients with early stage breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P2-01-11.

Tumor infiltrating lymphocytes in triple negative breast cancer receiving neoadjuvant chemotherapy

AIM

To determine influence of neoadjuvant-chemotherapy (NAC) over tumor-infiltrating-lymphocytes (TIL) in triple-negative-breast-cancer (TNBC).

METHODS

TILs were evaluated in 98 TNBC cases who came to Instituto Nacional de Enfermedades Neoplasicas from 2005 to 2010. Immunohistochemistry staining for CD3, CD4, CD8 and FOXP3 was performed in tissue microarrays (TMA) sections. Evaluation of H/E in full-face and immunohistochemistry in TMA sections was performed in pre and post-NAC samples. STATA software was used and P value < 0.05 was considered statistically significant.

RESULTS

Higher TIL evaluated in full-face sections from pre-NAC tumors was associated to pathologic-complete-response (pCR) (P = 0.0251) and outcome (P = 0.0334). TIL evaluated in TMA sections showed low level of agreement with full-face sections (ICC = 0.017-0.20) and was not associated to pCR or outcome. TIL in post-NAC samples were not associated to response or outcome. Post-NAC lesions with pCR had similar TIL levels than those without pCR (P = 0.6331). NAC produced a TIL decrease in full-face sections (P < 0.0001). Percentage of TIL subpopulations was correlated with their absolute counts. Higher counts of CD3, CD4, CD8 and FOXP3 in pre-NAC samples had longer disease-free-survival (DFS). Higher counts of CD3 in pre-NAC samples had longer overall-survival. Higher ratio of CD8/CD4 counts in pre-NAC was associated with pCR. Higher ratio of CD4/FOXP3 counts in pre-NAC was associated with longer DFS. Higher counts of CD4 in post-NAC samples were associated with pCR.

CONCLUSION

TIL in pre-NAC full-face sections in TNBC are correlated to longer survival. TIL in full-face differ from TMA sections, absolute count and percentage analysis of TIL subpopulation closely related.

The HER2 peptide nelipepimut-S (E75) vaccine (NeuVax™) in breast cancer patients at risk for recurrence: correlation of immunologic data with clinical response

Nelipepimut-S (formerly known as E75) is an immunogenic peptide from the HER2 protein that is highly expressed in breast cancer. The NeuVax™ (Galena, OR, USA) vaccine, nelipepimut-S plus granulocyte-macrophage colony-stimulating factor, is designed for the prevention of clinical recurrences in high risk, disease-free breast cancer patients. Although cancer vaccines such as NeuVax represent promising approaches to cancer immunotherapy, much remains to be elucidated regarding their mechanisms of action: particularly given that multiple cancer vaccine trials have failed to demonstrate a correlation between immunologic data and clinical outcome. Here, we briefly discuss our clinical trial experience with NeuVax focusing on immunologic response data and its implication on how the immune system may be affected by this peptide vaccine. Most importantly, we demonstrate the potential capability of certain immunologic assays to predict clinical benefit in our trials.

Influence of biospecimen variables on proteomic biomarkers in breast cancer

BACKGROUND

PI3K/Akt/mTOR signaling is being actively pursued as a therapeutic target for breast cancer. We sought to determine if tumor heterogeneity and biospecimen variables affect the evaluation of PI3K/Akt/mTOR pathway markers.

METHODS

Intraoperative image-guided core-needle biopsies (CNB), and central and peripheral surgical tumor specimens were prospectively collected in 53 patients with invasive breast cancer. Specimens were assessed with reverse-phase protein arrays (RPPA) and immunohistochemistry (IHC).

RESULTS

There was a moderate or strong correlation between the expression of 149 (97%) of the 154 different RPPA markers in the center and periphery. Correlation was higher for smaller tumors, in patients who did not undergo neoadjuvant therapy, and with shorter cold ischemia time. Of 154 markers, 132 (86%) were not statistically different between the center and periphery, and 97 (63%) were not different between the CNB and the surgical specimen (average of the central and peripheral specimen). pAkt S473 and PTEN had a significant correlation between central and peripheral specimens, and between CNB and surgical specimen. However, pAkt S473, pS6 S235/236, and pS6 240/244 levels were significantly higher in CNB than the central specimens both by RPPA and by IHC.

CONCLUSIONS

Most individual proteomic biomarkers studied do not have significant intratumoral heterogeneity. However, protein and phosphoprotein levels are affected by biospecimen type and other preanalytic variables. PI3K pathway activation is greater in CNB compared with postexcision surgical samples suggesting a potential loss of phosphorylation during surgical manipulation, or with cold ischemia of surgical specimens.

Immune checkpoints: A therapeutic target in triple negative breast cancer

Early clinical trials investigating monoclonal antibodies targeting the T-cell inhibitory receptor programmed cell death 1 (PD-1) and its ligand PD-L1 have shown efficacy in melanoma, non-small cell lung cancer and renal cell carcinoma. We recently demonstrated PD-L1 expression in 20% of triple negative breast cancers suggesting that targeting the PD-1/PD-L1 immune checkpoint may be an effective treatment modality in patients with this disease.

Abstract P1-02-07: Discordance for low and intermediate levels (1+ or 2+ by IHC) of HER2 protein expression in the phase III PRESENT trial

Background

Significant discordance has been described between different laboratories and between testing methodologies for HER2 overexpression and gene amplification. Concern has focused on missing patients who might benefit from treatment with HER2 targeted therapy. Concordance rates between local and central testing for tumors selected for HER2 0-2+ is not well described. We describe discordance rates between local and central testing performed to identify tumors with 1 and 2+ HER2 expression.

Methods

The PRESENT study is a multicenter, multinational, prospective, randomized, double-blind, controlled Phase 3 study assessing efficacy and safety of the peptide vaccine NeuVax, in HLA-A2 and/or A3 positive patients with early stage, node positive breast cancer expressing low and intermediate levels (1/2+ by IHC) of HER2 protein. PRESENT 2-step screening includes HLA testing followed by central lab confirmation of HER2 1 or 2+ expression using the DAKO HercepTest.

Results

215 patients underwent central IHC testing for HER2. Discordance between local and central testing was seen in 54% (117/215); 34% (65/192) of those eligible by local results were ineligible on central testing, and 48% (11/23) of those not eligible by local results were eligible on central testing.

Local testingCentral testing (IHC (%))IHC (n)01+2+3+0 (15)5 (33%)7 (47%3 (20%)—1+ (127)39 (31%)68 (53%)15 (12%)5 (4%)2+ (65)11 (17%)23 (35%)21 (32%)10 (16%)3+ (8)3 (38%)—1 (12%)4 (50%)

Of those with 1 or 2+ local results, 8% (15/192) were found to be 3+ on central testing. Discordant rates varied by geographic location with higher rates seen in Eastern Europe and Russia.

Conclusion

Significant discordance exists between local and central laboratory test results for HER2 expression by IHC even at lower levels of expression, and current tests are defined by their ability to determine 3+ positivity. In order to improve accuracy of testing and to develop a companion diagnostic for NeuVax, the Leica Bond Oracle HER2 IHC System will be incorporated into future HER2 screening for the PRESENT trial.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-02-07.

Abstract LB-218: Immune response assessment in a phase II trial of AE37 HER2 peptide vaccine

Introduction: AE37 is the Ii-Key hybrid of the HER2 derived peptide AE36 (776-790). A phase I trial administering AE37 with the immunoadjuvant GMCSF demonstrated the vaccine to be safe and capable of stimulating CD4+helper T cells with HER2 specific anti-tumor activity. Here we present an analysis of our immunologic testing of our prospective, randomized, single-blinded, phase II trial of the AE37+GMCSF vs. GMCSF alone for the prevention of breast cancer recurrence. Methods: After completion of indicated standard therapy; disease-free, node positive or high risk node negative breast cancer patients were randomized to receive either AE37+GMCSF (VG) or GMCSF (CG) in 6 monthly intradermal inoculations. Patients were enrolled with any level of HER2 expression (IHC 1+ 2+ or 3+). Specific immunologic responses to both AE36 and AE37 were evaluated. In vitro responses were measured using [3H]-thymidine incorporation assay and in vivo responses using delayed-type hypersensitivity (DTH) reactions. T regulatory cells (Tregs) were measured throughout vaccination series. Data was analyzed using Pearson chi-squared tests. Results: To date 217 patients have enrolled (VG=109, CG=108). HER2 over-expression was present in 54 (49.5%) VG and 51 (47.2%) CG, p=0.783. VG had 59 (51.4%) ER positive and CG had 58 (53.7%, p=0.985). The in vitro proliferation responses with a stimulation index (SI) ≥2 were classified as high responders VG 36 (33.0%) vs CG 8 (7.4%, p&lt;0.001), SI 1.5-2 were classified as low responders VG 19 (17.4%) vs CG 16 (14.8%, p=0.600) or SI &lt;1.5 as non responders VG 54(49.5%) vs CG 84(77.8%, p&lt;0.001). The in vivo DTH reactions measured in 149 (VG n=86, CG n=63) were stratified as responders with ≥5mm (VG 74(86.0%) vs CG 17(27.0%) p&lt;0.0001) or non responders with &lt;5mm (VG 12 (14.0%) vs CG 46(73.0%) p&lt;0.001). Tregs responses were measured in 107 patients (VG n=56, CG=51) and categorized according to percent change from pre-vaccination baseline as an increase &gt;110% (5(8.9%) VG vs 10 (19.6%) CG, p=0.112), no change 90-110% (10 (17.9%) VG vs 13 (25.5%) CG, p=0.337), or decrease &lt;90% (41 (73.2%) VG vs 28 (54.9%), p=0.048). Conclusion: VG patients had significant immunologic responses compared to CG. VG had a statistical decrease in Tregs compared to CG. Monitoring immunologic tests and Tregs throughout the vaccination process may stratify patients into responders and non responders and thus assist in identifying patients that will have recurrence.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr LB-218. doi:1538-7445.AM2012-LB-218

Abstract 788: Uptake and cross-presentation of the leukemia associated antigens neutrophil elastase (NE) and proteinase-3 (P3) increases susceptibility of solid tumors to PR1-targeted immunotherapy

We have shown that the HLA-A2-restricted nonapeptide PR1 (VLQELNVTV) is a leukemia-associated peptide derived from P3 and NE. Furthermore, immunologic and clinical responses to PR1 peptide vaccination occur in patients with acute (AML), chronic (CML) myeloid leukemia and myelodysplastic syndrome. We have also shown that PR1 expression results from NE and P3 cross-presentation by B-cells and dendritic cells. Because NE and P3 are present in lung and breast cancer tumor tissue, we investigated whether uptake of NE and P3 might result in PR1 expression on solid tumors, which could induce susceptibility of non-hematopoietic tumors to PR1-targeted immunotherapy. We studied melanoma, breast, ovarian and lung cancer cell lines to determine whether NE and P3 are cross-presented. Using flow cytometry, we show that numerous malignant cell lines take up 5 to 10 °g/ml of soluble NE and P3 and was dose- and time-dependent, consistent with a receptor-mediated mechanism. In addition to soluble NE and P3, uptake of granulocyte-associated NE and P3 was also demonstrated; however, uptake of soluble NE and P3 were 3- and 2-fold higher, when compared to granulocyte-associated proteins. Within 4 hours of uptake, confocal microscopy showed that soluble P3 localized to endosomes and lysosomes, suggesting the possibility of lysosomal degradation of P3, a common pathway for MHC-I processing of cross-presented proteins. With the use of 8F4, a monoclonal antibody that is specific for a PR1/HLA-A2 conformational epitope, we show that PR1/HLA-A2 is expressed by 12-hours on P3- and NE-pulsed HLA-A2+ melanoma and breast cancer cell lines. Because 8F4 mediates complement-dependent cytotoxicity (CDC) of AML, we studied whether PR1 expression induced susceptibility of P3- and NE-pulsed tumor cells to killing by 8F4 and PR1-CTL. Twelve hours after pulsing the HLA-A2+ breast cancer cell lines MDA-MB-453 and MDA-MB-231 with P3 or NE, up to 40% and 60% of pulsed breast cancer cells were lysed by PR1-CTL and 8F4, respectively. We conclude that PR1 is cross-presented by solid tumors following receptor-mediated uptake of soluble NE and P3 at concentrations observed in tumors and inflammatory sites. Importantly, this cross-presentation increased susceptibility of embryological distinct tumors to PR1-specific immunotherapy. Together, these data suggest that cross-presentation of extracellular inflammatory proteins that are normally not expressed in the tumor may be a mechanism shared by many tumors, which could be exploited by immunotherapy strategies targeting these proteins.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 788. doi:10.1158/1538-7445.AM2011-788

Interim Analysis of a Randomized Phase II Study of the Novel Ii-Key Hybrid HER2/Neu Peptide (AE37) Vaccine To Prevent Breast Cancer Recurrence: United States Military Cancer Institute Clinical Trials Group Study I-05

BACKGROUND: CD4+ T helper peptides from HER2/neu have been evaluated in vaccine trials. The Ii-Key addition, a 4-amino-acid (LRMK) modification, increases vaccine potency when compared to unmodified class II epitopes. We present results of a prospective, randomized, single-blinded phase II clinical trial of the Ii-Key hybrid HER2/neu peptide (AE37) + GM-CSF immunoadjuvant vaccine versus GM-CSF alone in the adjuvant setting in disease-free, high risk breast cancer (BCa) patients to prevent recurrence.METHODS: Disease-free, high risk BCa patients who have completed standard adjuvant therapy were enrolled and randomized to receive six monthly inoculations of either 500 mcg of AE37 with 62.5 or 125 mcg of GM-CSF (Peptide group; PG) or 62.5 or 125 mcg of GM-CSF alone (adjuvant group; AG). Toxicity was assessed after each inoculation using National Cancer Institute Common Terminology Criteria for Adverse Events v3.0 (CTCAE). Immunologic response was monitored using delayed type hypersensitivity reactions (DTH) and 3H-thymidine proliferative assays for both hybrid AE37 (LRMK+HER2/neu:776-790) and AE36 (unmodified HER2/neu:776-790) peptides. Patients were clinically, radiographically, and pathologically monitored for recurrence of BCa.RESULTS: Thus far, 120 (49 PG, 71 AG) of the planned 200 patients have completed the primary series. The PG and AG have similar demographic/prognostic characteristics (Table 1). Toxicity profiles in the PG and AG were almost identical with no grade 4-5 local toxicities and no grade 3-5 systemic toxicities in either arm. Median DTH reaction to AE36 and AE37 increased significantly from baseline at 1 month after completion of the primary series in the PG group (AE36: 0.0±0.8 cm to 15.3 ±2.1 cm; AE37: 0.0±0.7 cm to 24.5±2.6 cm; p&lt;0.0001) and did not change in the AG group (AE36: 0.0±0.5 cm to 0.0±1.4 cm; AE37: 0.0±0.7 cm to 0.0±1.6 cm; p&gt;0.05). Median proliferation response to AE36 and AE37 increased significantly from baseline at 3, 6, and 12 months after the start of the vaccine series in the PG (p&lt;0.015) and did not change significantly in the AG. At a median follow up of 13 months, there have been no (0.0%) recurrences in the PG (0/49) compared to 7.0% (5/71) in the AG (p=0.08).CONCLUSIONS: The modified peptide AE37 is safe with mild toxicities observed primarily due to the GM-CSF immunoadjuvant. AE37 elicits a strong HER2/neu-specific in-vivo and ex-vivo immune response to the modified and unmodified peptides. Importantly, the AE37 peptide vaccine may protect against BCa recurrences. peptideadjuvantp valueN=4971 Age (median)49520.06Node Positive75.5%62.1%0,16Grade 348.9%57.8%0.44Tumor ≥2 cm55.1%56.1%1ER/PR negative38.8%40.9%0.84HER2 over-expressor59.2%60.6%1 

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 3183.

NOTE: This abstract was accepted for presentation at the Symposium after the Abstract Book went to press.

Effect of modest delays in primary surgical treatment on progression of tumor size in breast cancer patients

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Background: Evaluation of medical co-morbidities, coordination of reconstructive surgery and referral to tertiary care centers can delay surgical treatment in breast cancer. These delays raise concerns for tumor progression in the interim. We evaluated the time from initial imaging at a cancer center to surgical treatment and the change in tumor size. Methods: We identified 823 patients who underwent surgery as their first therapeutic modality for invasive breast cancer diagnosed from December 2003 to September 2005. Baseline tumor size was determined by mammogram (MMG) and ultrasound (US) reports, and tumor size at surgery was determined by pathology reports. Results: The median time from imaging at our facility to surgery was 0.69 months (range 0.03 to 4.34). Multivariate modeling indicated that older patient age, undergoing total mastectomy, and undergoing reconstruction predicted a longer time from initial imaging to surgery. Comparing radiographic to pathologic size, a moderate correlation was demonstrated for both MMG (Spearman r = 0.58; p < 0.0001) and US (Spearman r = 0.66, p < 0.0001). Pathologic size was the same as MMG size in 14%, smaller in 49%, and larger in 37% of patients. Differences in tumor size estimates were not significantly associated with time lapse between MMG and surgery, but in a multivariate model, MMG tumor size, tumor histology, and tumor grade were significant predictors (p < 0.0001 for all) of differences in mammographic and pathologic size. The pathologic tumor size was the same as US in 10%, smaller in 38%, and larger in 52% of patients. Time lapse to surgery was not significantly associated with differences in US and pathologic tumor size. In a multivariate model, US tumor size (p < 0.0001), tumor histology (p = 0.0006) and tumor grade (p = 0.005) were significant predictors of differences in US and pathologic tumor size estimates. Conclusions: There is no evidence that time lapse from initial imaging to surgical intervention leads to significant changes in tumor size thus allowing patients to complete preoperative workup and planning without significant clinical disease progression.

No significant financial relationships to disclose.