Survival outcomes of patients with HER2/neu-positive breast cancer with germline BRCA mutations

BACKGROUND

Breast cancer (BC) with germline BRCA1/2 mutations and their association with triple-negative BC has been thoroughly investigated. However, some carriers of BRCA1/2 mutations have human epidermal growth factor receptor 2 (HER2/neu)-positive BC, which has a different targeted therapy approach, and data are scarce for this patient population. The authors sought to characterize the clinical characteristics and outcomes of patients with HER2/neu-positive BC who had germline BRCA1/2 mutations.

METHODS

This was a retrospective analysis of data from 1099 patients diagnosed with HER2/neu-positive BC who were screened for germline BRCA mutations between 1996 and 2022. Clinicopathologic features and survival rates were analyzed by BRCA mutation status. Univariate and multivariable Cox proportional hazards regression models were used to analyze the association between clinical variables and outcomes.

RESULTS

Of 1099 patients with HER2/neu-positive BC, 73 (6.6%) tested positive for BRCA1/2 mutations. Age, race, and tumor characteristics did not differ between BRCA noncarriers and carriers. At a median follow-up of 78.6 months, the 5-year recurrence-free survival rate was 85% in BRCA carriers and 87% in noncarriers (p = .79), and the 5-year overall survival rate was 94% in BRCA carriers and 94% in noncarriers (p = .78). In a multivariable model, BRCA was not associated with recurrence-free survival (hazard ratio, 0.99; 95% confidence interval, 0.51-1.90; p = .96) or overall survival (hazard ratio, 0.83; 95% confidence interval, 0.33-2.07; p = .69).

CONCLUSIONS

BRCA1/2 mutations occurred in 6.6% of patients with HER2/neu-positive BC and did not affect survival outcomes. Assessing the potential benefits of new treatment strategies, such as combining anti-HER2/neu therapies with poly(ADP-ribose) polymerase inhibitors, may lead to enhanced outcomes for these patients.

PTEN in triple-negative breast carcinoma: protein expression and genomic alteration in pretreatment and posttreatment specimens

Background

Recent advances have been made in targeting the phosphoinositide 3-kinase pathway in breast cancer. Phosphatase and tensin homolog (PTEN) is a key component of that pathway.

Objective

To understand the changes in PTEN expression over the course of the disease in patients with triple-negative breast cancer (TNBC) and whether PTEN copy number variation (CNV) by next-generation sequencing (NGS) can serve as an alternative to immunohistochemistry (IHC) to identify PTEN loss.

Methods

We compared PTEN expression by IHC between pretreatment tumors and residual tumors in the breast and lymph nodes after neoadjuvant chemotherapy in 96 patients enrolled in a TNBC clinical trial. A correlative analysis between PTEN protein expression and PTEN CNV by NGS was also performed.

Results

With a stringent cutoff for PTEN IHC scoring, PTEN expression was discordant between pretreatment and posttreatment primary tumors in 5% of patients (n = 96) and between posttreatment primary tumors and lymph node metastases in 9% (n = 33). A less stringent cutoff yielded similar discordance rates. Intratumoral heterogeneity for PTEN loss was observed in 7% of the patients. Among pretreatment tumors, PTEN copy numbers by whole exome sequencing (n = 72) were significantly higher in the PTEN-positive tumors by IHC compared with the IHC PTEN-loss tumors (p < 0.0001). However, PTEN-positive and PTEN-loss tumors by IHC overlapped in copy numbers: 14 of 60 PTEN-positive samples showed decreased copy numbers in the range of those of the PTEN-loss tumors.

Conclusion

Testing various specimens by IHC may generate different PTEN results in a small proportion of patients with TNBC; therefore, the decision of testing one versus multiple specimens in a clinical trial should be defined in the patient inclusion criteria. Although a distinct cutoff by which CNV differentiated PTEN-positive tumors from those with PTEN loss was not identified, higher copy number of PTEN may confer positive PTEN, whereas lower copy number of PTEN would necessitate additional testing by IHC to assess PTEN loss.

Trial registration

NCT02276443.

Predictive Roles of Baseline Stromal Tumor-Infiltrating Lymphocytes and Ki-67 in Pathologic Complete Response in an Early-Stage Triple-Negative Breast Cancer Prospective Trial

High stromal tumor-infiltrating lymphocytes (sTILs) are associated with improved pathologic complete response (pCR) in triple-negative breast cancer (TNBC). We hypothesize that integrating high sTILs and additional clinicopathologic features associated with pCR could enhance our ability to predict the group of patients on whom treatment de-escalation strategies could be tested. In this prospective early-stage TNBC neoadjuvant chemotherapy study, pretreatment biopsies from 408 patients were evaluated for their clinical and demographic features, as well as biomarkers including sTILs, Ki-67, PD-L1 and androgen receptor. Multivariate logistic regression models were developed to generate a computed response score to predict pCR. The pCR rate for the entire cohort was 41%. Recursive partitioning analysis identified ≥20% as the optimal cutoff for sTILs to denote 35% (143/408) of patients as having high sTILs, with a pCR rate of 59%, and 65% (265/408) of patients as having low sTILs, with a pCR rate of 31%. High Ki-67 (cutoff > 35%) was identified as the only predictor of pCR in addition to sTILs in the training set. This finding was verified in the testing set, where the highest computed response score encompassing both high sTILa and high Ki-67 predicted a pCR rate of 65%. Integrating Ki67 and sTIL may refine the selection of early stage TNBC patients for neoadjuvant clinical trials evaluating de-escalation strategies.

A phase II study of neoadjuvant atezolizumab and nab-paclitaxel in patients with anthracycline-resistant early-stage triple-negative breast cancer

PURPOSE

Neoadjuvant anti-PD-(L)1 therapy improves the pathological complete response (pCR) rate in unselected triple-negative breast cancer (TNBC). Given the potential for long-term morbidity from immune-related adverse events (irAEs), optimizing the risk-benefit ratio for these agents in the curative neoadjuvant setting is important. Suboptimal clinical response to initial neoadjuvant therapy (NAT) is associated with low rates of pCR (2-5%) and may define a patient selection strategy for neoadjuvant immune checkpoint blockade. We conducted a single-arm phase II study of atezolizumab and nab-paclitaxel as the second phase of NAT in patients with doxorubicin and cyclophosphamide (AC)-resistant TNBC (NCT02530489).

METHODS

Patients with stage I-III, AC-resistant TNBC, defined as disease progression or a < 80% reduction in tumor volume after 4 cycles of AC, were eligible. Patients received atezolizumab (1200 mg IV, Q3weeks × 4) and nab-paclitaxel (100 mg/m² IV,Q1 week × 12) as the second phase of NAT before undergoing surgery followed by adjuvant atezolizumab (1200 mg IV, Q3 weeks, × 4). A two-stage Gehan-type design was employed to detect an improvement in pCR/residual cancer burden class I (RCB-I) rate from 5 to 20%.

RESULTS

From 2/15/2016 through 1/29/2021, 37 patients with AC-resistant TNBC were enrolled. The pCR/RCB-I rate was 46%. No new safety signals were observed. Seven patients (19%) discontinued atezolizumab due to irAEs.

CONCLUSION

This study met its primary endpoint, demonstrating a promising signal of activity in this high-risk population (pCR/RCB-I = 46% vs 5% in historical controls), suggesting that a response-adapted approach to the utilization of neoadjuvant immunotherapy should be considered for further evaluation in a randomized clinical trial.

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

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

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

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

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

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

Tucatinib vs Placebo, Both in Combination With Trastuzumab and Capecitabine, for Previously Treated ERBB2 (HER2)-Positive Metastatic Breast Cancer in Patients With Brain Metastases: Updated Exploratory Analysis of the HER2CLIMB Randomized Clinical Trial

Importance

It is estimated that up to 50% of patients with ERBB2 (HER2)-positive metastatic breast cancer (MBC) will develop brain metastases (BMs), which is associated with poor prognosis. Previous reports of the HER2CLIMB trial have demonstrated that tucatinib in combination with trastuzumab and capecitabine provides survival and intracranial benefits for patients with ERBB2-positive MBC and BMs.

Objective

To describe overall survival (OS) and intracranial outcomes from tucatinib in combination with trastuzumab and capecitabine in patients with ERBB2-positive MBC and BMs with an additional 15.6 months of follow-up.

Design, Setting, and Participants

HER2CLIMB is an international, multicenter, randomized, double-blind, placebo-controlled clinical trial evaluating tucatinib in combination with trastuzumab and capecitabine. The 612 patients, including those with active or stable BMs, had ERBB2-positive MBC previously treated with trastuzumab, pertuzumab, and trastuzumab emtansine. The study was conducted from February 23, 2016, to May 3, 2019. Data from February 23, 2016, to February 8, 2021, were analyzed.

Interventions

Patients were randomized 2:1 to receive tucatinib (300 mg orally twice daily) or placebo (orally twice daily), both in combination with trastuzumab (6 mg/kg intravenously or subcutaneously every 3 weeks with an initial loading dose of 8 mg/kg) and capecitabine (1000 mg/m2 orally twice daily on days 1-14 of each 3-week cycle).

Main Outcomes and Measures

Evaluations in this exploratory subgroup analysis included OS and intracranial progression-free survival (CNS-PFS) in patients with BMs, confirmed intracranial objective response rate (ORR-IC) and duration of intracranial response (DOR-IC) in patients with measurable intracranial disease at baseline, and new brain lesion-free survival in all patients. Only OS was prespecified before the primary database lock.

Results

At baseline, 291 of 612 patients (47.5%) had BMs. Median age was 52 years (range, 22-75 years), and 289 (99.3%) were women. At median follow-up of 29.6 months (range, 0.1-52.9 months), median OS was 9.1 months longer in the tucatinib-combination group (21.6 months; 95% CI, 18.1-28.5) vs the placebo-combination group (12.5 months; 95% CI, 11.2-16.9). The tucatinib-combination group showed greater clinical benefit in CNS-PFS and ORR-IC compared with the placebo-combination group. The DOR-IC was 8.6 months (95% CI, 5.5-10.3 months) in the tucatinib-combination group and 3.0 months (95% CI, 3.0-10.3 months) in the placebo-combination group. Risk of developing new brain lesions as the site of first progression or death was reduced by 45.1% in the tucatinib-combination group vs the placebo-combination group (hazard ratio, 0.55 [95% CI, 0.36-0.85]).

Conclusions and Relevance

This subgroup analysis found that tucatinib in combination with trastuzumab and capecitabine improved OS while reducing the risk of developing new brain lesions, further supporting the importance of this treatment option for patients with ERBB2-positive MBC, including those with BMs.

Trial Registration

ClinicalTrials.gov Identifier: NCT02614794.

Preclinical and Clinical Efficacy of Trastuzumab Deruxtecan in Breast Cancer Brain Metastases

PURPOSE

Brain metastases can occur in up to 50% of patients with metastatic HER2-positive breast cancer. Because patients with active brain metastases were excluded from previous pivotal clinical trials, the central nervous system (CNS) activity of the antibody-drug conjugate trastuzumab deruxtecan (T-DXd) is not well characterized.

EXPERIMENTAL DESIGN

We studied how T-DXd affects growth and overall survival in orthotopic patient-derived xenografts (PDX) of HER2-positive and HER2-low breast cancer brain metastases (BCBM). Separately, we evaluated the effects of T-DXd in a retrospective cohort study of 17 patients with stable or active brain metastases.

RESULTS

T-DXd inhibited tumor growth and prolonged survival in orthotopic PDX models of HER2-positive (IHC 3+) and HER2-low (IHC 2+/FISH ratio < 2) BCBMs. T-DXd reduced tumor size and prolonged survival in a T-DM1-resistant HER2-positive BCBM PDX model. In a retrospective multi-institutional cohort study of 17 patients with predominantly HER2-positive BCBMs, the CNS objective response rate (ORR) was 73% (11/15) while extracranial response rate was 45% (5/11). In the subset of patients with untreated or progressive BCBM at baseline, the CNS ORR was 70% (7/10). The median time on treatment with T-DXd was 8.9 (1.3-16.2) months, with 42% (7/17) remaining on treatment at data cutoff.

CONCLUSIONS

T-DXd demonstrates evidence of CNS activity in HER2-positive and HER2-low PDX models of BCBM and preliminary evidence of clinical efficacy in a multi-institution case series of patients with BCBM. Prospective clinical trials to further evaluate CNS activity of T-DXd in patients with active brain metastases are warranted. See related commentary by Soffietti and Pellerino, p. 8.

Trastuzumab Deruxtecan in HER2-Positive Metastatic Breast Cancer Patients with Brain Metastases: A DESTINY-Breast01 Subgroup Analysis

DESTINY-Breast01 (NCT03248492) evaluated trastuzumab deruxtecan (T-DXd; DS-8201) in patients with heavily pretreated HER2-positive metastatic breast cancer (mBC). We present a subgroup of 24 patients with a history of treated brain metastases (BM), a population with limited treatment options. In patients with BMs, the confirmed objective response rate (cORR) was 58.3% [95% confidence interval (CI), 36.6%-77.9%], and the median progression-free survival (mPFS) was 18.1 months (95% CI, 6.7-18.1 months). In patients without BMs (n = 160), cORR was 61.3% and mPFS was 16.4 months. Eight patients (47.1%) experienced a best overall intracranial response of partial response or complete response. Seven patients (41.2%) had a best percentage change in brain lesion diameter from baseline consistent with stable disease. Two patients (8.3%) with BMs and two (1.3%) without BMs experienced progression in the brain. The safety profile of T-DXd was consistent with previous studies. The durable clinical activity of T-DXd in this population warrants further investigation.

SIGNIFICANCE

Advances in treating HER2-positive metastatic breast cancer have greatly improved patient outcomes, but intracranial progression remains an important risk for which few therapeutic options are currently available. T-DXd demonstrated durable efficacy in patients with stable, treated BMs. This article is highlighted in the In This Issue feature, p. 2711.

Molecular Characterization and Prospective Evaluation of Pathologic Response and Outcomes with Neoadjuvant Therapy in Metaplastic Triple-Negative Breast Cancer

PURPOSE

Metaplastic breast cancer (MpBC) is a rare subtype of breast cancer that is commonly triple-negative and poorly responsive to neoadjuvant therapy in retrospective studies.

EXPERIMENTAL DESIGN

To better define clinical outcomes and correlates of response, we analyzed the rate of pathologic complete response (pCR) to neoadjuvant therapy, survival outcomes, and genomic and transcriptomic profiles of the pretreatment tumors in a prospective clinical trial (NCT02276443). A total of 211 patients with triple-negative breast cancer (TNBC), including 39 with MpBC, received doxorubicin-cyclophosphamide-based neoadjuvant therapy.

RESULTS

Although not meeting the threshold for statistical significance, patients with MpBCs were less likely to experience a pCR (23% vs. 40%; P = 0.07), had shorter event-free survival (29.4 vs. 32.2 months, P = 0.15), metastasis-free survival (30.3 vs. 32.4 months, P = 0.22); and overall survival (32.6 vs. 34.3 months, P = 0.21). This heterogeneity is mirrored in the molecular profiling. Mutations in PI3KCA (23% vs. 9%, P = 0.07) and its pathway (41% vs. 18%, P = 0.02) were frequently observed and enriched in MpBCs. The gene expression profiles of each histologically defined subtype were distinguishable and characterized by distinctive gene signatures. Among nonmetaplastic (non-Mp) TNBCs, 10% possessed a metaplastic-like gene expression signature and had pCR rates and survival outcomes similar to MpBC.

CONCLUSIONS

Further investigations will determine if metaplastic-like tumors should be treated more similarly to MpBC in the clinic. The 23% pCR rate in this study suggests that patients with MpBC should be considered for NAT. To improve this rate, a pathway analysis predicted enrichment of histone deacetylase (HDAC) and RTK/MAPK pathways in MpBC, which may serve as new targetable vulnerabilities.

Abstract PD4-02: Safety and efficacy of a tucatinib-trastuzumab-capecitabine regimen for treatment of leptomeningeal metastasis (LM) in HER2-positive breast cancer: Results from TBCRC049, a phase 2 non-randomized study

Background: Treatment options for patients (pts) with leptomeningeal metastasis (LM) are limited, and the prognosis is poor (median overall survival (OS) ~ 4-5 months). Tucatinib is a potent and highly selective HER2-targeted tyrosine kinase inhibitor approved for use in combination with trastuzumab and capecitabine in pts with metastatic HER2+ breast cancer who have received ≥1 prior HER2-based regimen in the metastatic setting, including pts with brain metastases. TBCRC049 (NCT03501979) is an investigator-initiated, phase 2, single-arm study evaluating the safety and efficacy of tucatinib, trastuzumab and capecitabine in HER2+ breast cancer with newly diagnosed LM. We have previously demonstrated therapeutic levels of tucatinib in CSF in pts with HER2+ LM (Stringer-Reasor et al, ASCO 2021). We now report efficacy outcomes of the study. Methods: Eligible pts were adults with HER2+ metastatic breast cancer, Karnofsky performance status (KPS) &gt; 50, and newly diagnosed, untreated LM (defined as positive CSF cytology and/or radiographic evidence of LM, plus clinical signs/symptoms). Pts with treated or concurrent/new brain metastases were allowed. Pts received tucatinib 300 mg orally twice daily starting with cycle 1, day 1 (C1D1); capecitabine 1000 mg/m2 orally twice daily on days 1-14 of a 21-day cycle, starting on C1D1; and trastuzumab loading dose of 8 mg/kg IV on C1D1, and then 6 mg/kg IV once every 21 days, starting with C2D1. The primary endpoint was OS. Planned enrollment was 30 pts; however, due to lack of accrual since the FDA approval of tucatinib (4/2020), the study was closed after 17 patients were enrolled. Results: Baseline disease characteristics at LM diagnosis are shown in Table 1. Eight pts (47%) had abnormal CSF cytology (positive or equivocal). All pts had MRI evidence of LM in the brain, and 14/17 (82%) had brain metastases, of which 11 (65%) had received prior treatment for brain metastases. Median age at study treatment initiation was 53 years. Median number of treatment cycles received was 5 (range: 2-27). Median OS time was 11.9 months (95% CI: 4.1, NR). At data cutoff (6/22/21), 7/17 pts (41%) remained alive and median followup was 17 months(8-26). Median time to CNS progression was 6.9 months (95% CI: 2.8, 13.8). Conclusions: In pts with LMD from HER2+ metastatic breast cancer who were treated with tucatinib, trastuzumab, and capecitabine, the median OS time was nearly 1 year. This is the first prospective evidence of clinical benefit with a systemic regimen for HER2+ LM. Further studies evaluating brain-penetrant oral drugs in this rare pt population are needed.

Baseline Disease Characteristics (N=17)Number%Baseline CSF cytologyPositive529%Negative847%Equivocal318%None obtained1*6%Symptoms attributable to LMDYes1588%No212%MRI evidence of LMDBrain only1165%Brain and Spine635%History of brain metastasisYes1482%Prior treatment1165%New/concurrent diagnosis – no prior treatment318%No318%Extra-CNS DiseaseYes1165%No635%*One patient had VP shunt and difficulty sampling fluid; all CSF sent for research PK and non-PK studies

Citation Format: Rashmi K Murthy, Barbara O'Brien, Donald A Berry, Akshara Singareeka-Raghavendra, Maria Gule Monroe, Jason Johnson, Jason White, Jennifer Childress, Justin Sanford, Jill Schwartz-Gomez, Michelle Melisko, Aki Morikawa, Sherise Ferguson, John F de Groot, Ian Krop, Vicente Valero, Mothaffar Rimawi, Antonio Wolff, Debu Tripathy, Nancy U Lin, Erica Stringer-Reasor. Safety and efficacy of a tucatinib-trastuzumab-capecitabine regimen for treatment of leptomeningeal metastasis (LM) in HER2-positive breast cancer: Results from TBCRC049, a phase 2 non-randomized study [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 PD4-02.

Abstract PD4-04: Updated results of tucatinib vs placebo added to trastuzumab and capecitabine for patients with previously treated HER2-positive metastatic breast cancer with brain metastases (HER2CLIMB)

Background: Tucatinib is an oral tyrosine kinase inhibitor highly specific for HER2 that is approved for use in combination with trastuzumab and capecitabine in adults with advanced or metastatic HER2+ breast cancer, including patients with brain metastases, who have received one or more prior anti-HER2-based regimens in the metastatic setting. In the HER2CLIMB trial, the tucatinib regimen significantly prolonged progression-free survival (PFS) and overall survival (OS) in patients with HER2+ metastatic breast cancer (Murthy, NEJM 2020), including in patients with untreated, treated stable, and treated progressing brain metastases (Lin, J Clin Oncol, 2020). With an additional 15.6 months of follow-up, addition of tucatinib continued to show clinically meaningful prolongation of PFS and OS in the total study population (Curigliano, ASCO Meeting, 2021). We report updated results of exploratory efficacy analyses in patients with brain metastases. Methods: All patients in HER2CLIMB had a baseline brain MRI. Patients with brain metastases were eligible and classified as untreated, treated stable, or treated progressing. Patients were randomized 2:1 to receive tucatinib 300 mg twice daily or placebo, in combination with trastuzumab and capecitabine. Following the primary analysis, the protocol was amended to unblind sites to treatment assignment and allowed crossover from the placebo regimen to the tucatinib regimen. Efficacy analyses in patients with brain metastases at baseline were performed at approximately 2 years from the last patient randomized by applying RECIST 1.1 to the brain based on investigator evaluation. OS and CNS-PFS (progression in the brain or death) were evaluated in all patients with brain metastases. Patients without CNS-PFS events were censored at the last brain MRI. Confirmed intracranial (IC) objective response rate (ORR-IC) was evaluated in patients with measurable IC disease. Results: At a median follow-up of 29.6 months, median OS was 21.6 months vs 12.5 months in all patients with brain metastases (HR: 0.60; 95% CI: 0.44, 0.81), 21.4 months vs 11.8 months in patients with untreated/treated progressing brain metastases (HR: 0.52; 95% CI: 0.36, 0.77), and 21.6 months vs 16.4 months in patients with treated stable brain metastases (HR: 0.70; 95% CI: 0.42, 1.16). Median CNS-PFS was 9.9 months vs 4.2 months in all patients with brain metastases (HR: 0.39; 95% CI: 0.27, 0.56), 9.6 months vs 4.0 months in patients with untreated/treated progressing brain metastases (HR: 0.34; 95% CI: 0.22, 0.54), and 13.9 months vs 5.6 months in patients with treated stable brain metastases (HR: 0.41; 95% CI: 0.19, 0.85). ORR-IC was higher in the tucatinib arm (47.3%; 95% CI: 33.7, 61.2) vs the placebo arm (20.0%; 95% CI: 5.7, 43.7) for patients with brain metastases, and median duration of response (DOR) was 8.6 months (95% CI: 5.5, 10.3) vs 3.0 months (95% CI: 3.0, 10.3). Conclusions: With 15.6 months of additional follow-up, the tucatinib-trastuzumab-capecitabine regimen resulted in a robust and durable prolongation of OS for all patients with HER2+ metastatic breast cancer and brain metastases. Additionally, this benefit was maintained in patients with untreated/treated progressing and treated stable brain metastases. Treatment with tucatinib continued to show clinically meaningful benefit in CNS-PFS consistent with the primary analysis.

Citation Format: Nancy U Lin, Rashmi K Murthy, Vandana Abramson, Carey Anders, Thomas Bachelot, Philippe Bedard, Virginia Borges, David Cameron, David Cameron, Lisa Carey, A Jo Chien, Giuseppe Curigliano, Michael DiGiovanna, Karen Gelmon, Gabriel Hortobagyi, Sara Hurvitz, Ian Krop, Sherene Loi, Sibylle Loibl, Volkmar Mueller, Mafalda Oliveira, Elisavet Paplomata, Mark Pegram, Dennis Slamon, Amelia Zelnak, Jorge Ramos, Wentao Feng, Eric Winer. Updated results of tucatinib vs placebo added to trastuzumab and capecitabine for patients with previously treated HER2-positive metastatic breast cancer with brain metastases (HER2CLIMB) [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 PD4-04.

Abstract OT2-09-01: Phase I/II study of stereotactic radiation and abemaciclib in the management of hormone receptor positive HER2 negative breast cancer brain metastases

Background: Breast cancer patients with brain metastases have a high unmet clinical need and improved management strategies are needed. There has been interest in studying CDK 4/6 inhibitors in the management of breast cancer brain metastases. A phase II study has shown abemaciclib to have activity in the management of hormone receptor (HR)+/HER2- brain metastases. Pre-clinical data suggests a potential synergy with CDK inhibitors and radiation therapy. Stereotactic radiosurgery (SRS) is a cornerstone in the management of limited brain metastases. We hypothesize treatment with abemaciclib and SRS will be safe and improve intracranial progression free survival (PFS) compared to abemaciclib alone. Trial Design: The study is designed as a prospective, single-arm, nonrandomized, open-label, phase I/II trial of abemaciclib and endocrine therapy with SRS among patients with HR+/HER2- metastatic breast cancer brain metastases. Treatment will be initiated with one week of abemaciclib followed by stereotactic radiation to sites of brain metastases or post-operative cavities with continued abemaciclib. Safety will be monitored initially by a 3+3 design. If unexpected neurologic toxicities are noted, the dose of radiation therapy will be reduced. This will be followed by a phase II study to evaluate intracranial PFS. Eligibility: Eligible patients include those that are HR+/HER2-, ≥18, ECOG ≤2 with ≤15 breast cancer brain metastases with measurable disease per Response Assessment in Neuro-Oncology Brain Metastases (RANO-BM) criteria. Specific Aims: The primary objective of the phase I study is to evaluate the safety and feasibility of abemaciclib and SRS to sites of brain metastases in the management of HR+/HER2- metastatic breast cancer with brain metastases. The primary objective of the phase II portion is to determine PFS intracranially. Secondary objectives include evaluation of extracranial PFS, local and distant intracranial control, and overall survival. Statistical Methods: Safety and feasibility will be monitored in the phase I study using a 3 + 3 design followed by a phase II study to assess intracranial PFS. The phase II study is designed as a single-arm, two-stage trial using the Restricted-Kwak-and-Jung’s method. In the first stage, a total of 21 patients will be enrolled. If pre-specified endpoints are met, an additional 10 patients will be enrolled in the second stage. Patient Accrual: A total of up to 31 patients will be enrolled inclusive of patients in the phase I portion treated at the recommended phase II dose. Clinical trial information: NCT04923542.

Citation Format: Kamran A. Ahmed, Youngchul Kim, Michelle DeJesus, Sasha J. Beyer, Nicole O. Williams, Joshua Palmer, Kristina D. Woodhouse, Rashmi K. Murthy, Jing Li, Avan J. Armaghani, John A. Arrington, Ricardo L. Costa, Brian J. Czerniecki, Arnold B. Etame, Peter A. Forsyth, Hung T. Khong, Daniel E. Oliver, Marilin Rosa, Solmaz Sahebjam, Hatem H. Soliman, Aixa E. Soyano, Michael A. Vogelbaum, Michael Yu, Hyo S. Han. Phase I/II study of stereotactic radiation and abemaciclib in the management of hormone receptor positive HER2 negative breast cancer brain metastases [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 OT2-09-01.

Assessment of Residual Cancer Burden and Event-Free Survival in Neoadjuvant Treatment for High-risk Breast Cancer: An Analysis of Data From the I-SPY2 Randomized Clinical Trial

Importance

Residual cancer burden (RCB) distributions may improve the interpretation of efficacy in neoadjuvant breast cancer trials.

Objective

To compare RCB distributions between randomized control and investigational treatments within subtypes of breast cancer and explore the relationship with survival.

Design, Setting, and Participants

The I-SPY2 is a multicenter, platform adaptive, randomized clinical trial in the US that compares, by subtype, investigational agents in combination with chemotherapy vs chemotherapy alone in adult women with stage 2/3 breast cancer at high risk of early recurrence. Investigational treatments graduated in a prespecified subtype if there was 85% or greater predicted probability of higher rate of pathologic complete response (pCR) in a confirmatory, 300-patient, 1:1 randomized, neoadjuvant trial in that subtype. Evaluation of a secondary end point was reported from the 10 investigational agents tested in the I-SPY2 trial from March 200 through 2016, and analyzed as of September 9, 2020. The analysis plan included modeling of RCB within subtypes defined by hormone receptor (HR) and ERBB2 status and compared control treatments with investigational treatments that graduated and those that did not graduate.

Interventions

Neoadjuvant paclitaxel plus/minus 1 of several investigational agents for 12 weeks, then 12 weeks of cyclophosphamide/doxorubicin chemotherapy followed by surgery.

Main Outcomes and Measures

Residual cancer burden (pathological measure of residual disease) and event-free survival (EFS).

Results

A total of 938 women (mean [SD] age, 49 [11] years; 66 [7%] Asian, 103 [11%] Black, and 750 [80%] White individuals) from the first 10 investigational agents were included, with a median follow-up of 52 months (IQR, 29 months). Event-free survival worsened significantly per unit of RCB in every subtype of breast cancer (HR-positive/ERBB2-negative: hazard ratio [HZR], 1.75; 95% CI, 1.45-2.16; HR-positive/ERBB2-positive: HZR, 1.55; 95% CI, 1.18-2.05; HR-negative/ERBB2-positive: HZR, 2.39; 95% CI, 1.64-3.49; HR-negative/ERBB2-negative: HZR, 1.99; 95% CI, 1.71-2.31). Prognostic information from RCB was similar from treatments that graduated (HZR, 2.00; 95% CI, 1.57-2.55; 254 [27%]), did not graduate (HZR, 1.87; 95% CI, 1.61-2.17; 486 [52%]), or were control (HZR, 1.79; 95% CI, 1.42-2.26; 198 [21%]). Investigational treatments significantly lowered RCB in HR-negative/ERBB2-negative (graduated and nongraduated treatments) and ERBB2-positive subtypes (graduated treatments), with improved EFS (HZR, 0.61; 95% CI, 0.41-0.93) in the exploratory analysis.

Conclusions and Relevance

In this randomized clinical trial, the prognostic significance of RCB was consistent regardless of subtype and treatment. Effective neoadjuvant treatments shifted the distribution of RCB in addition to increasing pCR rate and appeared to improve EFS. Using a standardized quantitative method to measure response advances the interpretation of efficacy.

Trial Registration

ClinicalTrials.gov Identifier: NCT01042379.

Prognostic Model for De Novo and Recurrent Metastatic Breast Cancer

PURPOSE

Metastatic breast cancer (MBC) has a heterogeneous clinical course. We sought to develop a prognostic model for overall survival (OS) that incorporated contemporary tumor and clinical factors for estimating individual prognosis.

METHODS

We identified patients with MBC from our institution diagnosed between 1998 and 2017. We developed OS prognostic models by Cox regression using demographic, tumor, and treatment variables. We assessed model predictive accuracy and estimated annual OS probabilities. We evaluated model discrimination and prediction calibration using an external validation data set from the National Comprehensive Cancer Network.

RESULTS

We identified 10,655 patients. A model using age at diagnosis, race or ethnicity, hormone receptor and human epidermal growth factor receptor 2 subtype, de novo versus recurrent MBC categorized by metastasis-free interval, Karnofsky performance status, organ involvement, frontline biotherapy, frontline hormone therapy, and the interaction between variables significantly improved predictive accuracy (C-index, 0.731; 95% CI, 0.724 to 0.739) compared with a model with only hormone receptor and human epidermal growth factor receptor 2 status (C-index, 0.617; 95% CI, 0.609 to 0.626). The extended Cox regression model consisting of six independent models, for < 3, 3-14, 14-20, 20-33, 33-61, and ≥ 61 months, estimated up to 5 years of annual OS probabilities. The selected multifactor model had good discriminative ability but suboptimal calibration in the group of 2,334 National Comprehensive Cancer Network patients. A recalibration model that replaced the baseline survival function with the average of those from the training and validation data improved predictions across both data sets.

CONCLUSION

We have generated and validated a robust prognostic OS model for MBC. This model can be used in clinical decision making and stratification in clinical trials.

Abstract PS4-31: Characteristics of HER2/neu positive breast cancer among patients with and without germline BRCAmutations

Introduction: Breast cancer in BRCA 1/2 carriers is a well-characterized disease process, and its association with triple negative breast cancer has been extensively studied. In contrast, there is limited data on BRCA carriers and HER2/neu positive breast cancer, which identifies this topic as an area for further investigation. The BRCA protein plays an important role in DNA replication, whereas HER2/neu is a proto-oncogene that, when overexpressed, correlates with aggressive cancers. The relationship between these two mutations is poorly understood. There have been major strides with anti-HER2/neu therapies for HER2/neu positive disease and PARP inhibitors for BRCA germline positive patients, however there is a clinical knowledge gap in BRCA carriers who also have HER2/neu positive breast cancer. Further research into the characteristics of this population, treatment strategies, and outcomes is needed. More specifically, determining the utility of anti-HER2/neu therapies, PARP inhibitors, or the combination in this population could prove to have clinical utility. We aim to characterize the clinical characteristics, treatment strategies, and outcomes within this population.

Methods: Using a prospective research patient database at the UT MD Anderson Cancer Center 1038 patients were identified to have HER2/neu associated breast cancer who had undergone genetic counseling and testing for hereditary breast cancer syndromes between 1996 and 2019. This population was descriptively characterized to evaluate the prevalence of BRCA 1/2 positivity. Clinical and pathological characteristics as well as treatment, and recurrence were collected. Chi-square was used for statistical analysis. The Kaplan-Meier method was used to compare overall survival based on BRCA status.

Results: Amongst 1038 patients, germline BRCA mutation was detected in 49 (4.7%) of the patients. The median age at diagnosis for patients with BRCA mutations was significantly younger, 41.7 years (27-76), compared to 44.9 years (21-83) in the BRCA negative group (p= 0.0147). More patients were premenopausal in the BRCA positive group (p=0.027). Further characteristics are shown in Table 1. Overall survival was 71.6 months for the BRCA1 population, 81.3 months for the BRCA2 population, and 70.7 months for the BRCA negative population (p = 0.63). Recurrence free survival was 71 months for the BRCA1, 51.2 months for the BRCA2, and 59.6 months for the BRCA negative cohort (p = 0.4).

Conclusion: HER2/neu positive breast cancer patients with and without germline BRCA mutations have different clinical presentations. While we did not detect a survival difference due to small number of patients, this presents an opportunity to evaluate whether new treatment strategies, such as combining anti-HER2/neu therapies with PARP inhibitors can further improve outcomes for these patients.

Table 1:BRCA negativeBRCA positivep valuen%n%RaceASIAN666.724.10.0122BLACK979.8510.2HISPANIC16716.936.1NATIVE AMERICAN50.500.0OTHER111.148.2WHITE64365.03571.4Menopause Status at DxN/A40.400.00.0268POST17818.036.1PRE53454.03265.3Unknown27327.61428.6Age at Dxavg (range)44.9 (21-83)41.7 (27-76)0.0147Histology Typeductal93694.64591.80.3741lobular181.812.0mixed262.636.1other90.900.0StageI23523.81632.70.3293II46747.22040.8III28228.51224.5Unknown50.512.0Hormone Receptor StatusER and/or PR positive62663.33061.20.7271ER/PR negative35736.11938.8Unknown60.600.0Nuclear GradeI90.912.00.3474II22222.4714.3III69370.13673.5Unknown656.6510.2Ki67avg (range)40.5 (0-99)46 (10-90)0.1858Chemotypeadj32733.11632.70.2932neoadj56757.32551.0no chemo959.6816.3Herceptin Trxadj27027.31428.60.4093neoadj50651.22142.9none21121.31428.6unknown20.200.0Adj HormoneN44244.72449.00.5558Y54755.32551.0XRTN38038.42244.90.3637Y60961.62755.1989100.049100.0

Citation Format: Mihir A Shukla, Angelica Gutierrez Barrera, Stephen Karl Gruschkus, Rachel M Layman, Rashmi K Murthy, Banu K Arun. Characteristics of HER2/neu positive breast cancer among patients with and without germline BRCAmutations [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 PS4-31.

Abstract OT-34-01: Phase Ib/II trial of copanlisib in combination with trastuzumab and pertuzumab after induction treatment of HER2 positive metastatic breast cancer with PIK3CA mutation or PTEN mutation

Background:The PI3K/Akt/mTOR pathway is a critical regulator of cell growth, survival, and metabolism in cancer. Its activation plays an important role in resistance to chemotherapy and HER2 targeted therapy. PIK3CA activating mutations and PTEN loss were reported in 30% and 16% of BOLERO-1 and 32% and 12% of BOLERO-3 patients, respectively. Exploratory analyses suggested that the addition of everolimus to trastuzumab and chemotherapy improved progression free survival (PFS) in patients with PIK3CA mutations and PTEN loss. In the phase III CLEOPATRA trial, while the combination of pertuzumab (P) plus trastuzumab (H) plus docetaxel (T) as compared with trastuzumab (H) plus docetaxel (T), significantly prolonged PFS (18.5 vs 12.4 months) for first-line treatment for HER2-positive (+ve) metastatic breast cancer (MBC), longer median PFS was observed in patients with wildtype versus mutated PIK3CA in both the control (13.8 v 8.6 months) and pertuzumab groups (21.8 v 12.5 months). Copanlisib is a highly selective, class 1 pan-PI3K inhibitor with predominant activity against both the δ and α isoforms. It is currently FDA approved for the treatment of adults with relapsed follicular lymphoma. This study hypothesizes that the addition of copanlisib to dual HER2 targeted therapy after first line induction treatment will improve clinical outcomes in HER2 positive MBC patients with PIK3CA or PTEN genomic alterations. Trial Design: This is a randomized, two- arm, open label, phase-2 study to evaluate the clinical activity of copanlisib added to HP maintenance after induction with THP in HER2 +ve MBC patients with PIK3CA mutations or PTEN loss. A safety run-in cohort (phase 1B) will be performed. Copanlisib will be administered weekly on D1, D8 of a 21-day cycle. Eligibility criteriaHER2 +ve MBC based on ASCO-CAP criteria (HER2 status based on metastatic tissue)• Activating mutations in PIK3CA, or PTEN loss• ECOG performance status ≤1• Normal organ and marrow function• Within 8 weeks of completion of first-line induction therapy with THP (Phase-2). Any prior treatment provided eligible to receive THP induction (Phase-1B) Specific aimsTo assess the benefit of adding copanlisib to HP in HER2+ve MBC patients with PIK3CA mutations or PTEN loss after induction treatment (Phase-2)• To determine safety and recommended phase 2 dose (RP2D) of copanlisib, HP combination in HER2 MBC patients (Phase-1B)• To correlate PFS and OS with the triplet combination with the number of induction cycles, hormone receptor status, and PTEN loss by IHC• To identify potential predictive and prognostic biomarkers for copanlisib activity Statistical methodsThe primary objective of the phase-1B portion is to determine the RP2D for the combination of copanlisib, trastuzumab, and pertuzumab. Phase 1 portion will use a 3+3 dose de-escalation design. The primary objective of the phase 2 portion is to determine a difference in PFS with the addition of copanlisib to HP maintenance after induction. Projected median PFS in control group is 8 months and 16 months in the experimental arm. We aim to detect a HR of 0.50 with power of 0.90 with 1-sided alpha of 0.1. With a sample size of 82, 12 months post-accrual follow-up, and accrual rate of 5 patients per month, the study duration is 30 months. To have 82 evaluable patients with a 15% drop-out rate, we would need to enroll 96 patients. A Wieand rule futility interim analysis will be conducted when half of the total of 54 required PFS events are observed.

Citation Format: Senthil Damodaran, Rashmi K Murthy, Maliha Nusrat, Babita Saigal, Samantha C Trager, Debu Tripathy, Funda Meric-Bernstam. Phase Ib/II trial of copanlisib in combination with trastuzumab and pertuzumab after induction treatment of HER2 positive metastatic breast cancer with PIK3CA mutation or PTEN mutation [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-34-01.

Intracranial Efficacy and Survival With Tucatinib Plus Trastuzumab and Capecitabine for Previously Treated HER2-Positive Breast Cancer With Brain Metastases in the HER2CLIMB Trial

PURPOSE

In the HER2CLIMB study, patients with human epidermal growth factor receptor 2 (HER2)-positive breast cancer with brain metastases (BMs) showed statistically significant improvement in progression-free survival (PFS) with tucatinib. We describe exploratory analyses of intracranial efficacy and survival in participants with BMs.

PATIENTS AND METHODS

Patients were randomly assigned 2:1 to tucatinib or placebo, in combination with trastuzumab and capecitabine. All patients underwent baseline brain magnetic resonance imaging; those with BMs were classified as active or stable. Efficacy analyses were performed by applying RECIST 1.1 criteria to CNS target lesions by investigator assessment. CNS-PFS (intracranial progression or death) and overall survival (OS) were evaluated in all patients with BMs. Confirmed intracranial objective response rate (ORR-IC) was evaluated in patients with measurable intracranial disease.

RESULTS

There were 291 patients with BMs: 198 (48%) in the tucatinib arm and 93 (46%) in the control arm. The risk of intracranial progression or death was reduced by 68% in the tucatinib arm (hazard ratio [HR], 0.32; 95% CI, 0.22 to 0.48; P < .0001). Median CNS-PFS was 9.9 months in the tucatinib arm versus 4.2 months in the control arm. Risk of death was reduced by 42% in the tucatinib arm (OS HR, 0.58; 95% CI, 0.40 to 0.85; P = .005). Median OS was 18.1 versus 12.0 months. ORR-IC was higher in the tucatinib arm (47.3%; 95% CI, 33.7% to 61.2%) versus the control arm (20.0%; 95% CI, 5.7% to 43.7%; P = .03).

CONCLUSION

In patients with HER2-positive breast cancer with BMs, the addition of tucatinib to trastuzumab and capecitabine doubled ORR-IC, reduced risk of intracranial progression or death by two thirds, and reduced risk of death by nearly half. To our knowledge, this is the first regimen to demonstrate improved antitumor activity against BMs in patients with HER2-positive breast cancer in a randomized, controlled trial.

Results of a Randomized Phase IIb Trial of Nelipepimut-S + Trastuzumab versus Trastuzumab to Prevent Recurrences in Patients with High-Risk HER2 Low-Expressing Breast Cancer

PURPOSE

Preclinical data provide evidence for synergism between HER2-targeted peptide vaccines and trastuzumab. The efficacy of this combination was evaluated in patients with HER2 low-expressing breast cancer in the adjuvant setting.

PATIENTS AND METHODS

A phase IIb, multicenter, randomized, single-blinded, controlled trial enrolled disease-free patients after standard therapy completion (NCT01570036). Eligible patients were HLA-A2, A3, A24, and/or A26+, and had HER2 IHC 1+/2+, FISH nonamplified breast cancer, that was node positive and/or hormone receptor-negative [triple-negative breast cancer (TNBC)]. Patients received trastuzumab for 1 year and were randomized to placebo (GM-CSF, control) or nelipepimut-S (NPS) with GM-CSF. Primary outcome was 24-month disease-free survival (DFS). Secondary outcomes were 36-month DFS, safety, and immunologic response.

RESULTS

Overall, 275 patients were randomized; 136 received NPS with GM-CSF, and 139 received placebo with GM-CSF. There were no clinicopathologic differences between groups. Concurrent trastuzumab and NPS with GM-CSF was safe with no additional overall or cardiac toxicity compared with control. At median follow-up of 25.7 (interquartile range, 18.4-32.7) months, estimated DFS did not significantly differ between NPS and control [HR, 0.62; 95% confidence interval (CI), 0.31-1.25; P = 0.18]. In a planned exploratory analysis of patients with TNBC, DFS was improved for NPS versus control (HR, 0.26; 95% CI, 0.08-0.81, P = 0.01).

CONCLUSIONS

The combination of NPS with trastuzumab is safe. In HER2 low-expressing breast cancer, no significant difference in DFS was seen in the intention-to-treat analysis; however, significant clinical benefit was seen in patients with TNBC. These findings warrant further investigation in a phase III randomized trial.

Abstract OT2-01-02: TBCRC049: A phase II non-randomized study to assess the safety and efficacy of the combination of tucatinib and trastuzumab and capecitabine for treatment of leptomeningeal metastases in HER2 positive breast cancer TBCRC049: A phase II non-randomized study to assess the safety and efficacy of the combination of tucatinib and trastuzumab and capecitabine for treatment of leptomeningeal metastases in HER2 positive breast cancer

Background: Treatment options for patients with leptomeningeal disease (LMD) from HER2-positive breast cancer (HER2+ BC) are limited, and the prognosis is poor. Tucatinib is an oral, potent, HER2 specific tyrosine kinase inhibitor with good tolerability and notable early combinatory anti-tumor activity, including partial responses in heavily treated patients and those with parenchymal brain metastases (BM). Trial Design: This is a phase 2 single arm study to evaluate the efficacy of the combination of tucatinib plus trastuzumab (T) and capecitabine(C) in patients with HER2+ BC and newly diagnosed LMD. CNS disease will be evaluated at screening and every six weeks by MRI, CSF cytology, and neurological assessments according to RANO-LMD (adapted) and RANO-BM criteria. CT scans/PET-CT will evaluate extracranial disease according to RECIST criteria at screening and every 12 weeks. All patients will be followed for survival from the date of the last dose until death, lost to follow-up, or consent withdrawal. Symptom burden and quality of life assessments are conducted throughout the study. Blood and CSF sample collections occur at each cycle for the planned correlative analyses. Eligibility Criteria: Eligible patients are adults (&gt;18 years old) with HER2+ BC, ECOG status&lt;3/KPS&gt;50, and newly diagnosed untreated LMD (defined as positive CSF cytology and/or radiographic evidence of LMD, plus clinical signs/symptoms. Patients with a history of treated BM or concurrent/new BM are allowed. Patients previously treated with tucatinib or capecitabine (within the last 12 months) are excluded. Specific Aims: The primary endpoint is OS. Secondary endpoints include safety, CNS PFS at 12 weeks, RR and CBR in CNS and extra-CNS disease, and symptom burden/quality of life. Statistical methods: This study has a Gehan-like design with an interim futility analysis and overall intent to estimate OS. For the interim analysis, we define success to be CNS PFS for 12 weeks. An event will be considered to be either CNS progression or death from any cause before 12 weeks.We will stop enrollment if there are fewer than two successes in the first 15 patients. If the trial continues to completion, the regimen will be considered worthy of future study if the median overall survival is &gt; 4.4 months. Study Accrual: The target accrual is 30 patients. The study is currently active at UAB and MDACC. Other TBCRC sites throughout the country are to be activated this year.

Citation Format: Rashmi K Murthy, Barbara J O'Brien, Ken R Hess, Nick Navin, Jason Johnson, Maria Gule-Monroe, Jose P Leone, Jennifer Specht, Michelle Melisko, Aki Morikawa, Anna M Storniolo, Adam Brufsky, Paula R Pohlmann, Deric M Park, Ben H Park, Ian Krop, Nancy U Lin, Antonio Wolff, Andres Forerro-Torres, Erica Stringer-Reasor. TBCRC049: A phase II non-randomized study to assess the safety and efficacy of the combination of tucatinib and trastuzumab and capecitabine for treatment of leptomeningeal metastases in HER2 positive breast cancer TBCRC049: A phase II non-randomized study to assess the safety and efficacy of the combination of tucatinib and trastuzumab and capecitabine for treatment of leptomeningeal metastases in HER2 positive breast cancer [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 OT2-01-02.

Antitumor Activity and Safety of Trastuzumab Deruxtecan in Patients With HER2-Low-Expressing Advanced Breast Cancer: Results From a Phase Ib Study

PURPOSE

Trastuzumab deruxtecan (T-DXd, formerly DS-8201a) is a novel human epidermal growth factor receptor 2 (HER2)-targeted antibody drug conjugate (ADC) with a topoisomerase I inhibitor payload. A dose escalation and expansion phase I study evaluated the safety and activity of T-DXd in patients with advanced HER2-expressing/mutated solid tumors. Here, results for T-DXd at the recommended doses for expansion (RDE) in patients with HER2-low (immunohistochemistry [IHC] 1+ or IHC 2+/in situ hybridization-) breast cancer (ClinicalTrials.gov identifier: NCT02564900) are reported.

PATIENTS AND METHODS

Eligible patients had advanced/metastatic HER2-low-expressing breast cancer refractory to standard therapies. The RDE of 5.4 or 6.4 mg/kg T-DXd were administered intravenously once every 3 weeks until withdrawal of consent, unacceptable toxicity, or progressive disease. Antitumor activity and safety were assessed.

RESULTS

Between August 2016 and August 2018, 54 patients were enrolled and received ≥ 1 dose of T-DXd at the RDE. Patients were extensively pretreated (median, 7.5 prior therapies). The confirmed objective response rate by independent central review was 20/54 (37.0%; 95% CI, 24.3% to 51.3%) with median duration of response of 10.4 months (95% CI, 8.8 month to not evaluable). Most patients (53/54; 98.1%) experienced ≥ 1 treatment-emergent adverse event (TEAE; grade ≥ 3; 34/54; 63.0%). Common (≥ 5%) grade ≥ 3 TEAEs included decreases in neutrophil, platelet, and WBC counts; anemia; hypokalemia; AST increase; decreased appetite; and diarrhea. Three patients treated at 6.4 mg/kg suffered fatal events associated with T-DXd-induced interstitial lung disease (ILD)/pneumonitis as determined by an independent adjudication committee.

CONCLUSION

The novel HER2-targeted ADC, T-DXd, demonstrated promising preliminary antitumor activity in patients with HER2-low breast cancer. Most toxicities were GI or hematologic in nature. ILD is an important identified risk and should be monitored closely and proactively managed.

Tucatinib, Trastuzumab, and Capecitabine for HER2-Positive Metastatic Breast Cancer

BACKGROUND

Patients with human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer who have disease progression after therapy with multiple HER2-targeted agents have limited treatment options. Tucatinib is an investigational, oral, highly selective inhibitor of the HER2 tyrosine kinase.

METHODS

We randomly assigned patients with HER2-positive metastatic breast cancer previously treated with trastuzumab, pertuzumab, and trastuzumab emtansine, who had or did not have brain metastases, to receive either tucatinib or placebo, in combination with trastuzumab and capecitabine. The primary end point was progression-free survival among the first 480 patients who underwent randomization. Secondary end points, assessed in the total population (612 patients), included overall survival, progression-free survival among patients with brain metastases, confirmed objective response rate, and safety.

RESULTS

Progression-free survival at 1 year was 33.1% in the tucatinib-combination group and 12.3% in the placebo-combination group (hazard ratio for disease progression or death, 0.54; 95% confidence interval [CI], 0.42 to 0.71; P<0.001), and the median duration of progression-free survival was 7.8 months and 5.6 months, respectively. Overall survival at 2 years was 44.9% in the tucatinib-combination group and 26.6% in the placebo-combination group (hazard ratio for death, 0.66; 95% CI, 0.50 to 0.88; P = 0.005), and the median overall survival was 21.9 months and 17.4 months, respectively. Among the patients with brain metastases, progression-free survival at 1 year was 24.9% in the tucatinib-combination group and 0% in the placebo-combination group (hazard ratio, 0.48; 95% CI, 0.34 to 0.69; P<0.001), and the median progression-free survival was 7.6 months and 5.4 months, respectively. Common adverse events in the tucatinib group included diarrhea, palmar-plantar erythrodysesthesia syndrome, nausea, fatigue, and vomiting. Diarrhea and elevated aminotransferase levels of grade 3 or higher were more common in the tucatinib-combination group than in the placebo-combination group.

CONCLUSIONS

In heavily pretreated patients with HER2-positive metastatic breast cancer, including those with brain metastases, adding tucatinib to trastuzumab and capecitabine resulted in better progression-free survival and overall survival outcomes than adding placebo; the risks of diarrhea and elevated aminotransferase levels were higher with tucatinib. (Funded by Seattle Genetics; HER2CLIMB ClinicalTrials.gov number, NCT02614794.).

Prognostic Value of HER2 to CEP17 Ratio on Fluorescence In Situ Hybridization Ratio in Patients with Nonmetastatic HER2-Positive Inflammatory and Noninflammatory Breast Cancer Treated with Neoadjuvant Chemotherapy with or without Trastuzumab

BACKGROUND

We previously reported that in patients with HER2-positive (HER2+) locally advanced breast cancer treated with neoadjuvant trastuzumab-containing regimens, high HER2 to centromere enumerator probe 17 ratio on fluorescence in situ hybridization (HER2 FISH ratio) was an independent predictor of high pathologic complete response (pCR) rate, which translated into improved recurrence-free survival (RFS). We sought to determine whether high HER2 FISH ratio is a predictor of pCR and prognosis in patients with HER2+ nonmetastatic inflammatory breast cancer (IBC) and non-IBC treated with neoadjuvant chemotherapy with or without trastuzumab.

MATERIALS AND METHODS

This study included all patients with histologically proven stage III, HER2+ primary IBC, and non-IBC treated with neoadjuvant chemotherapy with or without trastuzumab and definitive surgery during 1999-2012. Univariate and multivariate logistic regression models were applied to assess the effect of covariates on pCR. Kaplan-Meier estimates with log-rank test were employed for survival analysis. Univariate and multivariate Cox proportional hazards models were used to assess the effect of covariates on RFS and overall survival (OS).

RESULTS

The study included 555 patients with stage III, HER+ breast cancer, 181 patients with IBC, and 374 with non-IBC. In the IBC cohort, HER2 FISH ratio was not significantly associated with pCR, RFS, or OS. In the non-IBC cohort, higher HER2 FISH ratio was significantly associated with higher pCR rate and longer OS.

CONCLUSION

HER2 FISH ratio showed prognostic value among patients with HER2+ non-IBC but not HER2+ IBC treated with neoadjuvant chemotherapy. This disparity may be due to the underlying aggressive nature of IBC.

IMPLICATIONS FOR PRACTICE

The findings of this study indicate that the HER2 to fluorescence in situ hybridization ratio as a continuous variable has promise as a predictor of pathologic complete response to neoadjuvant chemotherapy in patients with HER2-positive (HER2+) noninflammatory breast cancer (non-IBC) regardless of the results on HER2 immunohistochemical testing. In the future, some patients with HER2+ non-IBC and a high HER2 FISH ratio might even be offered personalized treatment options, such as nonsurgical treatment.

Neoadjuvant Talazoparib for Patients With Operable Breast Cancer With a Germline BRCA Pathogenic Variant

PURPOSE

Talazoparib has demonstrated efficacy in patients with BRCA-positive metastatic breast cancer. This study evaluated the pathologic response of talazoparib alone for 6 months in patients with a known germline BRCA pathogenic variant (gBRCA-positive) and operable breast cancer.

METHODS

Eligibility included 1 cm or larger invasive tumor and gBRCA-positive disease. Human epidermal growth factor receptor 2-positive tumors were excluded. Twenty patients underwent a pretreatment biopsy, 6 months of once per day oral talazoparib (1 mg), followed by definitive surgery. Patients received adjuvant therapy at physician's discretion. The primary end point was residual cancer burden (RCB). With 20 patients, the RCB-0 plus RCB-I response rate can be estimated with a 95% CI with half width less than 20%.

RESULTS

Twenty patients were enrolled from August 2016 to September 2017. Median age was 38 years (range, 23 to 58 years); 16 patients were gBRCA1 positive and 4 patients were gBRCA2 positive. Fifteen patients had triple-negative breast cancer (estrogen receptor/progesterone receptor < 10%), and five had hormone receptor-positive disease. Five patients had clinical stage I disease, 12 had stage II, and three had stage III, including one patient with inflammatory breast carcinoma and one with metaplastic chondrosarcomatous carcinoma. One patient chose to receive chemotherapy before surgery and was not included in RCB analyses. RCB-0 (pathologic complete response) rate was 53% and RCB-0/I was 63%. Eight patients (40%) had grade 3 anemia and required a transfusion, three patients had grade 3 neutropenia, and 1 patient had grade 4 thrombocytopenia. Common grade 1 or 2 toxicities were nausea, fatigue, neutropenia, alopecia, dizziness, and dyspnea. Toxicities were managed by dose reduction and transfusions. Nine patients required dose reduction.

CONCLUSION

Neoadjuvant single-agent oral talazoparib once per day for 6 months without chemotherapy produced substantial RCB-0 rate with manageable toxicity. The substantive pathologic response to single-agent talazoparib supports the larger, ongoing neoadjuvant trial (ClinicalTrials.gov identifier: NCT03499353).

LPTO-09. INTRATHECAL TOPOTECAN FOR LEPTOMENINGEAL METASTASIS IN SOLID TUMORS: THE MD ANDERSON EXPERIENCE

BACKGROUND: Leptomeningeal metastasis (LM) is a devastating complication of cancer resulting in progressive neurologic decline. Although intrathecal (IT) methotrexate and cytarabine are commonly used for solid tumor LM, we routinely use IT topotecan due to previously demonstrated similar efficacy and modest side effect profile. We report updated data on our experience. METHODS: We reviewed clinical records of patients with solid tumor LM treated with IT topotecan at MD Anderson Cancer Center from 2008–2018. Patient characteristics and course were summarized by descriptive statistics. Overall survival (OS) was estimated with Kaplan-Meier, and the association of KPS with OS evaluated with log-rank test. RESULTS: 138 patients were treated with IT topotecan. The median age was 54 years (range, 22–76), 81% were female. Breast cancer (62%) was the most common primary, then lung (21%), melanoma (4%). Median time from primary diagnosis to LM was 3.4 (range, 0.07–25.2) years. LM was diagnosed by CSF cytology alone in 8 (6%), MRI alone in 21 (15%), CSF+MRI in 108 (78%). Patients most commonly presented with headache (39%) or sensory changes (18%), and had a median KPS of 80 (range, 60–100). 66% had prior/concurrent brain metastasis. 71 patients (52%) received WBRT following LM diagnosis. 41% had adverse effects, most commonly nausea/vomiting (22%) and headache (20%). The majority were grade 1 (63%); 7 were grade 4 (2 Ommaya malfunctions and 5 infections). Patients received a median of 9 (range, 1–79) doses, most stopped due to CNS progression (42%). Median OS was 6.5 months (95% CI 4.7, 7.8). OS was 3.8 mos with KPS ≤70, vs. 7.5 mos with KPS >70 (p< 0.001). CONCLUSIONS: IT topotecan has a modest side effect profile. Patients with higher functional status at diagnosis had significantly better survival. This study supports the continued use of IT topotecan as a well-tolerated option for LM.

MLTI-10. ESTABLISHMENT OF A MULTIDISCIPLINARY BRAIN METASTASIS CLINIC TO FACILITATE PATIENT-CENTERED CARE AND COORDINATED RESEARCH

BACKGROUND: ~30% cancer patients develop brain metastases (BM), reflected by ~1600 BM patients treated at MD Anderson Cancer Center annually. With advances in systemic therapy and extracranial disease control, BM is a growing challenge. Multi-disciplinary BM management is critical and complex requiring coordination of multiple oncology sub-specialties. There is limited data on pragmatic clinic models to streamline and advance care. METHODS: Recognizing deficiency in BM treatment and research, a steering committee was formed at MDACC to establish an interdisciplinary BM clinic (BMC), with a multi-disciplinary BM research retreat held in 2016. The goal of BMC was to centralize patient referrals, improve patient outcomes and experience, and advance research by developing clinical trials and biomarker discovery programs. Meetings were held to address BMC format, workflow, EMR integration, data collection infrastructure, and staffing model. RESULTS: MDACC BMC clinic opened in 01/2019 with two half-day clinics staffed by neurosurgery, neuro-radiation oncology, neuro-radiology and medical/neuro oncology. A dedicated advanced practice provider screens the referrals according to a well-developed algorithm. A multidisciplinary conference is held immediately before each clinic where patient images are reviewed, cases are discussed and consensus recommendations are developed. The treatment plan and follow up appointments are arranged at the completion of the clinic visit to expedite care. ~50 patients have been seen with excellent patient satisfaction response and reduced time to treatment. ~20% patients had major change in treatment plan following multi-disciplinary evaluation. Additional efforts to develop a central BM database along with clinical and translational research programs are on-going. CONCLUSIONS: Establishment of a multi-disciplinary BMC to facilitate care and centralize research programs addresses a critical need for coordinated patient-centered BM management. This endeavor has enhanced patient experience through multi-specialty collaboration. Our program demonstrates the feasibility and effectiveness of a dedicated BMC in the treatment of this complex patient population.

LPTO-08. INTRATHECAL TRASTUZUMAB PLUS/MINUS IT TOPOTECAN FOR PATIENTS WITH HER2+ BREAST CANCER AND LEPTOMENINGEAL METASTASIS

BACKGROUND: Leptomeningeal metastasis (LM) is an aggressive complication of cancer. No standard therapies exist, although at our institution we commonly use IT topotecan in good-risk patients. We report our experience in patients with HER2+ breast cancer (BC) LM treated with intrathecal (IT) trastuzumab +/- IT topotecan. METHODS: We retrospectively reviewed records of patients managed with IT trastuzumab at MD Anderson Cancer Center from 2016–2019. Demographics, clinical course, and outcomes data (Kaplan-Meier) were collected and analyzed. RESULTS: 14 female patients (median age 49, range 33–67) with HER2+ BC (29% hormone receptor (HR) positive, 71% negative) were treated with IT trastuzumab (titrated to 40 mg -100 mg/week); 8 (57%) received concurrent IT topotecan. LM diagnosis was made in 64% by MRI alone, and 36% by both MRI and CSF cytology; 79% had brain metastases (BM), and of those, 55% (6/11) had active BM at LM diagnosis; 57% received WBRT prior to initiation of IT therapy. Median KPS was 90 (range, 60–100). Of those with initially positive cytology, 50% (4/8) converted to negative during treatment. MRI findings improved in 79%; 79% were symptomatic at diagnosis (most commonly ataxia, cranial neuropathy, headache); 70% (7/10) had symptom improvement on IT therapy. The only IT-associated symptom reported was mild nausea that occurred in 29%. Median time from diagnosis of metastatic BC was 10.7 mos. (range 0–83 mos); 36% had active extra-CNS disease and 86% received concurrent systemic therapy; 57% underwent change in systemic therapy during IT treatment; 91% were progression-free at 6 months, 32% at 24 months. Median overall survival from LM diagnosis was 24.7 months (95% CI 10.7, NR). CONCLUSIONS: IT trastuzumab is a safe and promising therapy for patients with HER2+ BC and LM. Dual IT therapy with trastuzumab and topotecan was well-tolerated and warrants further investigation in a larger study.

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

BACKGROUND

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

METHODS

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

RESULTS

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

DISCUSSION

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

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

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

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

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

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

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

Abstract OT2-07-08: Withdrawn

This abstract was withdrawn by the authors.

Citation Format: Paplomata E, Borges V, Loi S, Abramson V, Hamilton E, Hurvitz S, Lin N, Walker L, Murthy RK. Withdrawn [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr OT2-07-08.

Abstract P2-09-01: Subgroups analysis of a multicenter, prospective, randomized, blinded phase 2b trial of trastuzumab + nelipeptimut-S (NeuVax) vs trastuzumab for prevention of recurrence in breast cancer patients

Background:HER2 low-expressing (LE) (IHC 1-2+, FISH non-amplified) breast cancer (BC) patients (pts) have not benefited from HER2-directed therapy despite HER2 antigen availability. Triple negative BC (TNBC), in particular, is immunogenic and in need of additional therapeutic options. We have previously shown the HER2-derived nelipeptimut-S (E75) + GM-CSF (NeuVax) to be synergistic with trastuzumab (Tz) in pre-clinical and pilot clinical studies. In a planned interim analysis of a multi-center, prospective, randomized, single-blinded, placebo-controlled phase 2b trial of Tz + NeuVax vs Tz to reduce recurrence in HER2 LE, node-positive (NP) and/or triple negative BC (TNBC) pts, we previously reported that the NeuVax + Tz was safe without added cardiac toxicity and demonstrated a significant reduction of recurrences in TNBC pts. This analysis examines additional subsets in this trial.

Methods:HER2 LE, NP and/or TNBC pts who were clinically disease-free after standard therapy were randomized to receive Tz+NeuVax (vaccine group; VG) or Tz+GM-CSF (control group; CG). All pts received 1 yr of Tz per label. NeuVax or GM-CSF was given every 3 weeks x 6 starting with the 3rdTz dose, and then boosted every 6 months x 4. This pre-specified interim analysis was triggered 6 months after last enrollment. The primary endpoint is intention-to-treat 24 month disease-free survival (DFS) evaluated by log rank.

Results: Of 275 pts randomized in the study (VG n=136, CG n=139), 98 had TNBC (VG=53, CG=45). In the interim analysis, estimated disease-free survival (DFS) was assessed with a median follow up of 18.8 months. No significant clinicopathologic differences were seen between treatment groups. In the TNBC group, estimated DFS was higher overall in VG vs CG (91.9% v 69.9%, p=0.023; hazard ratio [HR] 0.29, 95% confidence interval [CI] 0.09-0.90). On TNBC subgroup analysis, estimated DFS was higher in VG vs CG among pts who received neoadjuvant chemotherapy (VG n=35, CG n=31; HR 0.26, CI 0.07-0.93; p=0.03), HER2 IHC 1+ BC (VG n=34, CG n=28; HR 0.20, CI 0.04-0.96; p=0.03), pts who were AJCC 7thedition stage I/II (VG n=37, CG n=27; HR incalculable, no recurrences in the VG, p=0.008), and pts 351yr of age (VG n=32 & CG n = 26; HR 0.26 CI 0.07,0.94; p=0.009). HRs did not appreciably vary based on the histologic grade or presence of lymphovascular invasion.

Conclusion:Examining the subgroups from the pre-specified interim analysis demonstrates a highly significant clinical benefit in TNBC pts overall. Within the TNBC cohort, specific benefit was seen in pts who received chemotherapy neoadjuvantly, expressed lower HER2, were earlier stage, and were older in age. These factors may help enrich the TNBC population targeted in a definitive Phase 3 study in TNBC patients with residual disease after neoadjuvant chemotherapy.

Citation Format: Clifton GT, Kemp Bohan PM, Hale DF, Myers JW, Brown TA, Holmes JP, Vreeland TJ, Litton JK, Murthy RK, Mittendorf EA, Peoples GE. Subgroups analysis of a multicenter, prospective, randomized, blinded phase 2b trial of trastuzumab + nelipeptimut-S (NeuVax) vs trastuzumab for prevention of recurrence in breast cancer patients [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-09-01.

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

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

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

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

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

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

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

Advances in HER2-Targeted Therapy: Novel Agents and Opportunities Beyond Breast and Gastric Cancer

The introduction of HER2-targeted therapy for breast and gastric patients with ERBB2 (HER2) amplification/overexpression has led to dramatic improvements in oncologic outcomes. In the past 20 years, five HER2-targeted therapies have been FDA approved, with four approved in the past 8 years. HER2-targeted therapy similarly was found to improve outcomes in HER2-positive gastric cancer. Over the past decade, with the introduction of next-generation sequencing into clinical practice, our understanding of HER2 biology has dramatically improved. We have recognized that HER2 amplification is not limited to breast and gastric cancer but is also found in a variety of tumor types such as colon cancer, bladder cancer, and biliary cancer. Furthermore, HER2-targeted therapy has signal of activity in several tumor types. In addition to HER2 amplification and overexpression, there is also increased recognition of activating HER2 mutations and their potential therapeutic relevance. Furthermore, there is a rapidly growing number of new therapeutics targeting HER2 including small-molecule inhibitors, antibody-drug conjugates, and bispecific antibodies. Taken together, an increasing number of patients are likely to benefit from approved and emerging HER2-targeted therapies.

Comparative Effectiveness of an mTOR-Based Systemic Therapy Regimen in Advanced, Metaplastic and Nonmetaplastic Triple-Negative Breast Cancer

BACKGROUND

Triple-negative breast cancer (TNBC) is a heterogeneous disease with subtypes having different "targetable" molecular aberrations. Metaplastic breast cancers (MpBCs) are typically TNBCs and commonly have alterations in the PI3K/Akt/mTOR pathway. We previously reported efficacy for an mTOR-based chemotherapy regimen in MpBC. To determine if tumor subtype influences prognosis, we compared treatment outcomes of patients with MpBC with those of patients with nonmetaplastic TNBC receiving an mTOR-based systemic therapy regimen.

PATIENTS AND METHODS

Patients with advanced MpBC and nonmetaplastic TNBC were treated at our institution from April 16, 2009, through November 4, 2014, using mTOR inhibition (temsirolimus or everolimus) with liposomal doxorubicin and bevacizumab (DAT/DAE). Median progression-free survival (PFS) and overall survival (OS) were estimated by the Kaplan-Meier method. Cox regression analyses were used to evaluate associations between tumor histology and outcomes. Multivariable models were adjusted for all covariates.

RESULTS

Fourteen patients with nonmetaplastic TNBC and 59 patients with advanced MpBC were treated with DAT/DAE. MpBC patients were older (p = .002) and less likely to have a history of bevacizumab use (p = .023). Median PFS for the nonmetaplastic TNBC and MpBC patients was 2.5 months and 4.8 months, respectively. This difference in PFS was statistically significant on univariable (p = .006) but not multivariable analysis (p = .087). Median OS for the nonmetaplastic TNBC and MpBC patients was 3.7 months and 10.0 months, respectively (p = .0003). MpBC remained significantly associated with improved OS on multivariable analysis (p < .0001).

CONCLUSION

In our study, DAT/DAE appeared to be more effective in MpBC compared with nonmetaplastic TNBC. These data support patient selection for targeted therapy in TNBC.

IMPLICATIONS FOR PRACTICE

Metaplastic breast cancers (MpBCs) represent <1% of all breast cancers, demonstrate mesenchymal differentiation, and are typically resistant to chemotherapy. Patients with advanced MpBC treated with an mTOR-based systemic therapy regimen had better long-term outcomes compared with patients with nonmetaplastic triple-negative breast cancer treated with the same regimen, suggesting that metaplastic histology may predict benefit from agents targeting the PI3K/Akt/mTOR pathway.

Long-Term Survival of De Novo Stage IV Human Epidermal Growth Receptor 2 (HER2) Positive Breast Cancers Treated with HER2-Targeted Therapy

BACKGROUND

An increasing proportion of human epidermal growth receptor 2 (HER2) positive (HER2+) metastatic breast cancer (MBC) is diagnosed as de novo stage IV disease. We hypothesize that a subset of these patients who achieve no evidence of disease (NED) status after multimodality HER2-targeted treatments may have prolonged progression-free survival (PFS) and overall survival (OS).

MATERIALS AND METHODS

Patients with de novo stage IV, HER2+ MBC (n = 483) diagnosed between 1998 and 2015 were identified at two institutions (Yale and MD Anderson Cancer Centers). Clinical variables, treatment details, and survival outcomes were compared between those who achieved NED and those who did not.

RESULTS

All patients received trastuzumab, and 20% also received pertuzumab as first-line therapy. The median OS was 5.5 years (95% confidence interval [Cl]: 4.8-6.2). Sixty-three patients (13.0%) achieved NED; their PFS and OS rates were 100% and 98% (95% CI: 94.6%-100%), respectively, at 5 years and remained the same at 10 years. For patients with no NED (n = 420), the PFS and OS rates were 12% (95% CI: 4.5%-30.4%) and 45% (95% CI: 38.4%-52.0%) at 5 years and 0% and 4% (95% CI, 1.3%-13.2%) at 10 years, respectively. NED patients more frequently had solitary metastasis (79% vs. 51%, p = .005) and surgery to resect cancer (59% vs. 22%, p ≤ .001). In multivariate analysis, NED status (hazard ratio [HR]: 0.014, p = .0002) and estrogen receptor positive status (HR: 0.72; p = .04) were associated with prolonged OS.

CONCLUSION

Among patients with de novo stage IV, HER2+ MBC, those who achieve NED status have a very high PFS and OS. Further randomized studies are required to fully understand the impact of systemic or locoregional therapy on achieving these excellent long-term outcomes.

IMPLICATIONS FOR PRACTICE

In this retrospective review at two institutions, it was demonstrated that 13% of patients with de novo stage IV, human epidermal growth receptor 2 positive metastatic breast cancer achieved no evidence of disease (NED) status with trastuzumab-based therapy plus/minus local therapies, and these patients had a very high progression-free survival (100%) and overall survival (98%) at both the 5- and 10-year time points. Achieving NED status may be an important therapeutic goal. However, further randomized studies are required to fully understand the impact of systemic or locoregional therapy on achieving these excellent long-term outcomes.

Genetic Counseling Referral Rates in Long-Term Survivors of Triple-Negative Breast Cancer

Background: Inherited BRCA gene mutations (pathogenic variants) cause 10% of breast cancers. BRCA pathogenic variants predispose carriers to triple-negative breast cancer (TNBC); around 30% of patients with TNBC carry BRCA pathogenic variants. The 2018 NCCN Guidelines for Genetic/Familial High-Risk Assessment: Breast and Ovarian recommend genetic counseling referrals for patients with TNBC diagnosed at age ≤60 years. This study sought to describe genetic counseling referral patterns among long-term TNBC survivors at The University of Texas MD Anderson Cancer Center. Methods: This single-institution retrospective analysis of female long-term (disease-free for ≥5 years) TNBC survivors sought to determine the rate of genetic counseling referral among patients diagnosed at age ≤60 years between 1992 and 2008. Patients who underwent treatment and surveillance visits at our institution and were followed until 2017 were included. We collected BRCA pathogenic variant status among tested patients. Descriptive statistical methods and a univariate analysis were used to identify patient characteristics associated with genetic counseling referral. Results: We identified 646 female long-term TNBC survivors with a median age at diagnosis of 47 years. Of these, 245 (38%) received a recommendation for a genetic counseling referral. Among those referred, 156 (64%) underwent genetic testing, and 35% of those tested had BRCA pathogenic variants. Interestingly, among those referred, 20% declined genetic testing. The rate of genetic referrals improved over time, from 25% among TNBC survivors whose last surveillance visit was between 2011 and 2013 to 100% among those whose last surveillance visit was between 2014 or later. Younger age and premenopausal status at diagnosis and a family history of breast or ovarian cancer were associated with an increased rate of referral for genetic counseling. Conclusions: Among long-term TNBC survivors, the rate of referral to genetic counseling increased over time, and among those tested, 35% carried a BRCA pathogenic variant. Survivorship care provides an excellent opportunity to refer eligible patients for genetic counseling.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Abstract P6-03-04: Central nervous system miliary metastasis in breast cancer patients

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

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

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

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

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

Citation Format: Bashour SI, Ibrahim NK, Schomer DF, Colen RR, Sawaya R, Suki D, Rao G, Murthy RK, Moulder SL, Abugabal Y, Hess KR, Fuller GN. Central nervous system miliary metastasis in breast cancer patients [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P6-03-04.

A phase II study of tipifarnib and gemcitabine in metastatic breast cancer

Background Tipifarnib is an orally active, competitive inhibitor of farnesyltransferase which has shown encouraging signs of activity either alone or when combined with other agents. Clinical studies of tipifarnib in combination with anti-estrogen therapy have yielded disappointing results. In contrast, tipifarnib appears to be synergistic in combination with anthracycline based chemotherapy. Here we report the results of the first prospective phase II trial evaluating the efficacy of the novel combination of tipifarnib and gemcitabine in the treatment of metastatic breast cancer. Patients and Methods 30 postmenopausal women with metastatic breast cancer were treated on a 21-day cycle with tipifarnib 300 mg PO twice daily from days 1 through 14. Gemcitabine was administered intravenously at a dose of 1000 mg/m² on days 1 and 8. Patients were treated until disease progression or unacceptable toxicity. Results There was one complete response and four partial responses yielding an objective response rate of 16.7%. Median progression-free survival and overall survival was 2.5 months (95% confidence interval: 1.6-5.7 months) and 13.1 months (95% confidence interval: 9.1-20.6 months), respectively. 40% of patients experienced grade 4 neutropenia in this study. Conclusion The combination of tipifarnib and gemcitabine is not well tolerated with high rates of myelosuppression and is not more effective than gemcitabine monotherapy in the treatment of metastatic breast cancer.

A feasibility study of neoadjuvant talazoparib for operable breast cancer patients with a germline BRCA mutation demonstrates marked activity

This study was undertaken to determine the feasibility of enrolling breast cancer patients on a single-agent-targeted therapy trial before neoadjuvant chemotherapy. Specifically, we evaluated talazoparib in patients harboring a deleterious BRCA mutation (BRCA+). Patients with a germline BRCA mutation and ≥1 cm, HER2-negative primary tumors were eligible. Study participants underwent a pretreatment biopsy, 2 months of talazoparib, off-study core biopsy, anthracycline, and taxane-based chemotherapy ± carboplatin, followed by surgery. Volumetric changes in tumor size were determined by ultrasound at 1 and 2 months of therapy. Success was defined as 20 patients accrued within 2 years and <33% experienced a grade 4 toxicity. The study was stopped early after 13 patients (BRCA1 + n = 10; BRCA2 + n = 3) were accrued within 8 months with no grade 4 toxicities and only one patient requiring dose reduction due to grade 3 neutropenia. The median age was 40 years (range 25–55) and clinical stage included I (n = 2), II (n = 9), and III (n = 2). Most tumors (n = 9) were hormone receptor-negative, and one of these was metaplastic. Decreases in tumor volume occurred in all patients following 2 months of talazoparib; the median was 88% (range 30–98%). Common toxicities were neutropenia, anemia, thrombocytopenia, nausea, dizziness, and fatigue. Single-agent-targeted therapy trials are feasible in BRCA+ patients. Given the rapid rate of accrual, profound response and favorable toxicity profile, the feasibility study was modified into a phase II study to determine pathologic complete response rates after 4–6 months of single-agent talazoparib.

An investigational PARP inhibitor seems safe and possibly effective when given ahead of surgery to women with BRCA-mutated breast cancer. Jennifer Litton and colleagues from the University of Texas MD Anderson Cancer Center in Houston, USA, conducted a small feasibility study to see if patients with stage I-III breast cancer and inherited mutations in BRCA1 or BRCA2 would put off their standard course of chemotherapy ahead of surgery to first receive two months of talazoparib, an experimental inhibitor of poly ADP ribose polymerase (PARP), an enzyme involved in DNA damage repair. The trial was a resounding success. In fact, owing to rapid patient enrollment, decreases in tumor volume among all 13 participants and few signs of serious side effects, the researchers amended the study protocol to give talazoparib for longer and test for therapeutic efficacy.

Abstract 1796: A targeted RNA-seq assay to measure activating ER mutations and ER/PR-associated gene expression predicts sensitivity to endocrine therapy for metastatic breast cancer

Background: We developed SET4 as a targeted, droplet-based, next-generation RNA sequencing assay to measure both the SETER/PR index of gene expression and the percent of estrogen receptor (ER) transcripts with point mutation in the ligand-binding domain (LBD) in metastatic biopsies of Stage IV breast cancer. The SETER/PR index (31 genes) is a cumulative measure of gene expression for transcripts associated with ER and progesterone receptor (PR), excluding those with a direct role in proliferation. High SETER/PR could indicate increased sensitivity to endocrine therapy, whereas LBD mutations indicate resistance but might also induce high SETER/PR.

Methods: Targeted needle biopsies from a metastatic site were prospectively obtained from 82 patients with HR+/HER2- breast cancer at time of any progression event, and preserved in RNAlater. Samples were prepared for targeted sequencing on a MiSeq by combining purified total RNA with SET4 primers and RT-PCR master mix into single molecule-formatted picodroplets using a RainDrop Source instrument, followed by thermal cycling and sample indexing. Calculated SETER/PR index and percent ER transcripts with LBD mutations were evaluated as continuous variables and compared to progression-free and overall survival using Cox regression analysis with log-rank test, if the next treatment after biopsy included endocrine therapy.

Results: The average read depth for the LBD of the ER transcript was 33,475X (range: 1230-180,889X), confidently detecting mutation at 1% frequency. LBD mutations were identified in 17% (14/82) of metastases (range of mutated transcripts 1%-98%). LBD mutations (&gt;10% of transcripts) were only observed in metastases with higher SETER/PR (above the median). In patients who next received endocrine therapy (n=58), higher SETER/PR predicted longer progression-free (PFS) (HR=0.37, p=0.0004, Δ median PFS 9 months) and overall survival (OS) (HR=0.49, p=0.03). The predictions were more pronounced in patients without LBD mutation (PFS HR=0.32, p=0.0001, Δ median PFS 13 months; OS HR=0.42, p=0.01). Currently, there are insufficient cases with LBD mutation for reliable survival analysis.

Conclusion: The SET4 assay measured the percent of ER transcripts with activating LBD mutation (≥1% prevalence) and also downstream ER/PR-related transcription. High SETER/PR predicted longer PFS and OS with endocrine therapy. While activating LBD mutations may be associated with endocrine resistance of Stage IV cancer, they were associated with high SETER/PR index. Consequently, metastatic cancers with high SETER/PR index and no LBD mutation in ER transcripts were particularly sensitive to endocrine therapy. This single assay unraveled a possible interaction between genotype, phenotype, and treatment outcome; and is currently being evaluated in a larger cohort of patients.

Citation Format: Rosanna Lau, Lily Fu, Michael Samuels, Rashmi K. Murthy, Bruno Sinn, Jane Yu, Rebekah Gould, Jennifer Litton, Alda Tam, Stacy Moulder, Daniel Booser, Debu Tripathy, Vicente Valero, Fraser Symmans. A targeted RNA-seq assay to measure activating ER mutations and ER/PR-associated gene expression predicts sensitivity to endocrine therapy for metastatic breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1796. doi:10.1158/1538-7445.AM2017-1796

Targeting the PI3K/AKT/mTOR Pathway for the Treatment of Mesenchymal Triple-Negative Breast Cancer: Evidence From a Phase 1 Trial of mTOR Inhibition in Combination With Liposomal Doxorubicin and Bevacizumab

Importance

Triple-negative breast cancer (TNBC) classified by transcriptional profiling as the mesenchymal subtype frequently harbors aberrations in the phosphoinositide 3-kinase (PI3K) pathway, raising the possibility of targeting this pathway to enhance chemotherapy response. Up to 30% of mesenchymal TNBC can be classified histologically as metaplastic breast cancer, a chemorefractory group of tumors with a mixture of epithelial and mesenchymal components identifiable by light microscopy. While assays to identify mesenchymal TNBC are under development, metaplastic breast cancer serves as a clinically identifiable surrogate to evaluate potential regimens for mesenchymal TNBC.

Objective

To assess safety and efficacy of mammalian target of rapamycin (mTOR) inhibition in combination with liposomal doxorubicin and bevacizumab in patients with advanced metaplastic TNBC.

Design, Setting, and Participants

Phase 1 study with dose escalation and dose expansion at the University of Texas MD Anderson Cancer Center of patients with advanced metaplastic TNBC. Patients were enrolled from April 16, 2009, to November 4, 2014, and followed for outcomes with a cutoff date of November 1, 2015, for data analysis.

Interventions

Liposomal doxorubicin, bevacizumab, and the mTOR inhibitors temsirolimus or everolimus using 21-day cycles.

Main Outcomes and Measures

Safety and response. When available, archived tissue was evaluated for aberrations in the PI3K pathway.

Results

Fifty-two women with metaplastic TNBC (median age, 58 years; range, 37-79 years) were treated with liposomal doxorubicin, bevacizumab, and temsirolimus (DAT) (N = 39) or liposomal doxorubicin, bevacizumab, and everolimus (DAE) (N = 13). The objective response rate was 21% (complete response = 4 [8%]; partial response = 7 [13%]) and 10 (19%) patients had stable disease for at least 6 months, for a clinical benefit rate of 40%. Tissue was available for testing in 43 patients, and 32 (74%) had a PI3K pathway aberration. Presence of PI3K pathway aberration was associated with a significant improvement in objective response rate (31% vs 0%; P = .04) but not clinical benefit rate (44% vs 45%; P > .99).

Conclusions and Relevance

Using metaplastic TNBC as a surrogate for mesenchymal TNBC, DAT and DAE had notable activity in mesenchymal TNBC. Objective response was limited to patients with PI3K pathway aberration. A randomized trial should be performed to test DAT and DAE for metaplastic TNBC, as well as nonmetaplastic, mesenchymal TNBC, especially when PI3K pathway aberrations are identified.

Abstract P6-09-35: Proposal for a new breast cancer staging classification: Incorporating clinical and biologic factors

Background: The current breast cancer staging system, based on anatomy, does not always reflect the variable clinical course outcomes seen in the clinic. Other important and known determinants of prognosis and survival in breast cancer are age, grade, and receptor subtypes. In this analysis, we sought to demonstrate that these additional factors were important determinants of breast cancer specific and overall survival with an intention to propose a new staging classification. Methods: Through a prospectively maintained electronic database at the University of Texas MD Anderson Cancer Center, we identified patients with newly diagnosed invasive breast cancer, stage I-IV, who received surgery as an initial treatment from 1997 to 2014. Data points for the earliest invasive breast cancer event were recorded: age, pathologic stage (7th edition AJCC), grade, ER status, PR status, HER2-neu status, adjuvant treatment history, and outcomes (breast cancer-specific survival [BCSS] and overall survival [OS]). Cox proportional hazards model was used for the statistical analysis. Results: Of 22,131 patients, 99% were women in the following age groups (median age at surgery, 53 years [range, 16-98 years]): age &lt; 40 (13%), 40-69 (76%), &gt;70 (11%). Pathologic stages were: I: 50%, II: 39%, III: 9% and IV: 2%; 768 (3.5%) patients had bilateral breast cancer. Biological subtypes were as follows: Triple-negative (TN): 6%, Hormone receptor-positive/HER2-negative (HR+/HER2-): 70%, HER2-positive (HER2+): 24% (HR+, 9%; HR- 15%). Median follow-up was 7.9 years (95% CI, 7.8-8.0). In multivariate Cox regression modeling, age, grade, and clinical biomarker-based subtypes were significantly associated with breast cancer specific survival (BCSS).

Table 1. Breast cancer specific-survival: Multivariate modelCovariateLevelHR95% CI (p value)Overall p valueAge at DiagnosisLess than 401.521.37-1.68 (&lt;.0001) 40-69Reference&lt;.0001 70-791.050.89-1.24 (0.55) Over 801.150.79-1.66 (0.47)Pathologic StageIAReference&lt;.0001 IIB0.880.58-1.32 (0.54) IIA2.201.96-2.46 (&lt;.0001) IIB3.453.06-3.89 (&lt;.0001) IIIA4.293.70-4.96 (&lt;.0001) IIIB3.432.45-4.79 (&lt;.0001) IIIC6.585.52-7.84 (&lt;.0001) IV15.1212.72-17.96 (&lt;.0001)Biologic SubtypeHR+, HER2-Reference&lt;.0001 HR+, HER2+*0.580.46-0.73 (&lt;.0001) HR-, HER2+*1.100.90-1.35 (0.35) TN**2.001.82-2.21 (&lt;.0001)Nuclear GradeIReference&lt;.0001 II1.731.34-2.23 (&lt;.0001) III3.292.55-4.24 (&lt;.0001)*All patients were treated with trastuzumab in the adjuvant setting **Considering TN as the reference (HR (95% CI): HR+/HER2- (0.50 (0.45-0.55)), HR+/HER2+ (0.29 (0.23-0.37)), HR-/HER2+ (0.55(0.45-0.68). Abbreviations - BCSS: HR: hazard ratio, CI: confidence interval, HR+: hormone receptor positive, HR-: hormone receptor negative, HER2+: Her2-neu positive, HER2-: HER2-neu negative, TN: triple negative, Reference: 1.00

Conclusion: More individualized prediction of outcomes for breast cancer is possible by considering clinical and biologic characteristics in addition to anatomic stage. We intend to integrate pathologic stage, age, and biologic factors into a novel prognostic model to propose a new staging classification for breast cancer.

Citation Format: Murthy RK, Song J, Raghavendra AS, Li Y, Hsu L, Barcenas CH, Tripathy D, Berry D, Hortobagyi GN. Proposal for a new breast cancer staging classification: Incorporating clinical and biologic factors [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 P6-09-35.

Phase I Study of ONT-380, a HER2 Inhibitor, in Patients with HER2+-Advanced Solid Tumors, with an Expansion Cohort in HER2+ Metastatic Breast Cancer (MBC)

Purpose: ONT-380 (ARRY-380) is a potent and selective oral HER2 inhibitor. This Phase I study determined the MTD, pharmacokinetics (PK) and antitumor activity of ONT-380 in HER2-positive advanced solid tumors, with an expansion cohort of patients with HER2⁺ MBC.Experimental Design: ONT-380 was administered twice daily (BID) in continuous 28-day cycles. After a modified 3+3 dose-escalation design determined the MTD, the expansion cohort was enrolled. PK properties of ONT-380 and a metabolite were determined. Response was evaluated by Response Evaluation Criteria in Solid Tumors (RECIST).Results: Fifty patients received ONT-380 (escalation = 33; expansion = 17); 43 patients had HER2⁺ MBC. Median prior anticancer regimens = 5. Dose-limiting toxicities of increased transaminases occurred at 800 mg BID, thus 600 mg BID was the MTD. Common AEs were usually Grade 1/2 in severity and included nausea (56%), diarrhea (52%), fatigue (50%), vomiting (40%) constipation, pain in extremity and cough (20% each). 5 patients (19%) treated at MTD had grade 3 AEs (increased transaminases, rash, night sweats, anemia, and hypokalemia). The half-life of ONT-380 was 5.38 hours and increases in exposure were approximately dose proportional. In evaluable HER2⁺ MBC (n = 22) treated at doses ≥ MTD, the response rate was 14% [all partial response (PR)] and the clinical benefit rate (PR + stable disease ≥ 24 weeks) was 27%.Conclusions: ONT-380 had a lower incidence and severity of diarrhea and rash than that typically associated with current dual HER2/EGFR inhibitors and showed notable antitumor activity in heavily pretreated HER2⁺ MBC patients, supporting its continued development. Clin Cancer Res; 23(14); 3529-36. ©2017 AACR.