Abstract ES5-1: Tumor dormancy and recurrence

Despite early detection and adjuvant therapy, breast cancer remains the leading cause of cancer mortality in women, largely due to distant, incurable recurrences that arise years, or even decades, after treatment of the primary tumor. Recurrent, metastatic tumors arise from the pool of residual local and disseminated tumor cells (DTCs) that survive primary treatment in tissues at sites throughout the body where they persist in a presumed dormant state. Early studies demonstrated that an immunohistochemical assay can detect cytokeratin-positive DTCs in bone marrow aspirates of a substantial fraction of breast cancer patients lacking any clinical signs of metastasis. Importantly, women who harbor detectable DTCs in their bone marrow have a substantially increased risk of distant recurrence, as well as poorer breast cancer-specific and overall survival, and this measure has repeatedly been shown to be an independent predictor of recurrence-free survival and overall survival in multivariate analysis.

Since DTCs constitute the reservoir from which recurrent cancers arise, understanding their biology is a critical priority in cancer research. We hypothesize that effectively disabling the survival mechanisms by which DTCs persist in breast cancer patients following treatment will deplete this critical reservoir of cells, reduce tumor recurrence, and thereby improve survival. At present, however, the mechanisms enabling these cells to survive in a dormant state and ultimately recur are poorly understood and clinical methods to detect DTCs, as well as DTC-directed therapeutic approaches, are still in their infancy.

To address this critical gap and elucidate critical pathways in dormant tumor cell survival, we and others have developed a variety of mouse models for human breast cancer that recapitulate key features of human breast cancer progression, including metastasis, residual disease, dormancy and recurrence. Investigation of these models using both genetic and pharmacological approaches has identified several mediators of dormant DTC survival and recurrence, demonstrated their relevance to pathways that contribute to therapeutic resistance in human breast cancers following targeted therapy or chemotherapy, and revealed that pharmacological targets for dormancy and recurrence may be unique to these stages of tumor progression. These findings have, in turn, led to the initiation of clinical trials to test the ability of targeted therapies to deplete the burden of DTCs in the bone marrow of breast cancer patients and thereby decrease risk of relapse. If successful, the ability to therapeutically target survival mechanisms utilized by DTCs would constitute a powerful, paradigm-shifting approach to preventing cancer recurrence and the mortality associated with it.

Citation Format: Chodosh L. Tumor dormancy and recurrence [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 ES5-1.

Abstract OT2-06-03: METAMORPH: METAstatic markers of recurrent tumor PHenotype for breast cancer

Up to 30% of patients diagnosed with breast cancer will develop recurrent disease within their lifetime, and currently this form of the disease is incurable. There are unmet needs to better understand underlying metastatic biology, identify new therapeutic targets and develop better methods for monitoring changes in disease, both to monitor response and elucidate resistance mechanisms. To address these needs, the METAMORPH Study encompasses a comprehensive approach that combines serial molecular tissue profiling at the RNA and DNA level with circulating markers (DTCs, CTCs, plasma tumor DNA), and ongoing assessment of therapeutic response.

METAMORPH is a prospective cohort study of women with suspected or confirmed recurrent breast cancer and accessible tumor by standard clinical biopsy, who are enrolled at the University of Pennsylvania prior to starting a new therapy for recurrent metastatic disease. The aims of this trial are to (1) evaluate the mechanisms through which recurrent breast cancer are genetically distinct from the primary tumor, (2) evaluate the circulating tumor biomarker trajectory of recurrent disease, (3) elucidate “escape pathways” of progressing tumors that emerge during the selective pressure of therapy, and (4) explore clinical utility of tumor and blood testing. The study protocol integrates research aims into clinical care, including a standardized approach to disease assessment and biopsy, pathologic confirmation of histology and receptor subtype, panel-based CLIA-approved genomic profiling, collection of research specimens, and standardized reporting of results, which are returned to patients and physicians. Patients are followed for treatment and outcome, and serial samples are collected at progression. A companion protocol, COMET, provides education about genomic testing and assesses patient understanding and impact of results. To date, 155 patients have enrolled, 142 (92%) have been biopsied, 120 (77%) have had sufficient DNA for molecular profiling and 109 (70%) have had genomic panel testing. Accrual is ongoing, with an initial target of 300 patients. Multiple sites within the UPHS Health System are enrolling. Contact information: angela.demichele@uphs.upenn.edu.

Key words: Metastatic disease, tumor profiling.

Citation Format: DeMichele A, Soucier-Ernst DJ, Clark C, Shih N, Stavropoulos W, Maxwell KN, Feldman M, Lierbamen D, Morrissette JJD, Paul MR, Pan T-C, Wang J, Belka GK, Chen Y, Yee S, Carpenter E, Fox K, Matro J, Clark A, Shah P, Domchek S, Bradbury A, Chodosh L. METAMORPH: METAstatic markers of recurrent tumor PHenotype for 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 OT2-06-03.

Abstract P6-07-05: Mutational spectrum and tumor response in metastatic breast cancer

Background: While several comprehensive genomic sequencing tests are clinically available for breast cancer(BC), little is known about the spectrum of findings reported in the general population and clinical utility of findings for patients(pts). Here we report tumor sequencing from the METAMORPH study, a comprehensive genomic testing approach in pts with metastatic(met) BC.

Methods: Pts with either known or suspected BC mets consented to and clinically underwent concurrent diagnostic and research tumor biopsies(bx). FFPE specimens were profiled via Illumina TruSeq Cancer Panel next generation sequencing platform covering 212 amplicons in 47 cancer genes. Pathology, treatment and outcome data were prospectively collected and tracked. Aside from Her2-directed treatment, therapy was not mutation (mut)-matched.

Results: 64 pts enrolled between 11/2013 – 05/2015. Of these, 48 had bx successfully sequenced (75%). Of those without sequencing, 5 had negative/insufficient tissue, 2 had insufficient DNA, remainder no bx/pending. Median age of those sequenced was 56 (range 31-78); 81% Caucasian, 17% African American. 25% (12 pts) presented with de novo stage IV disease. Of those with recurrence (n=36), 83% had prior adjuvant chemotherapy; 81% hormone receptor positive(HR+) had prior endocrine therapy. Median # prior lines of therapy for met disease was 2 (IQR 0 – 8). Tumor characteristics, including mut analyses, are shown in Table 1. # muts did not differ significantly by subtype(p=0.22). Frequency of TP53 and PIK3CA hotspot muts was nearly identical to TCGA. Median # muts was 1 for pts with both de novo mets and recurrence(p=0.79). # of muts was not associated with time to recurrence(p=0.80). Excluding pts found to have TP53 mut only or ERBB2 alterations in known Her2+ disease, 42% of pts were identified as having at least one potentially actionable alteration (PIK3CA mut, AKT1 mut or EGFR amplification). Median time to treatment failure(TTF) on subsequent therapy was 4.1 months for overall group, and 4.1, 6.2, and 1.6 months for HR+/Her2-, any Her2+ and TN, respectively, adjusted for line of therapy(p=0.03). After adjustment for # lines of prior met therapy, TTF was 4.7 vs. 4.1 months for pts with any mut vs. none(p=0.89); 5.7 vs 4.1 months for PIK3CA+ vs. not (p=0.94); 3.3 vs. 6.5 months for TP53+ vs. not (p=0.03).

Conclusion: Pts with met BC have frequent and potentially actionable muts.While overall # of muts did not affect response, tumors with TP53 muts had shorter response to subsequent therapy in this cohort. Additional data are needed to determine the clinical utility of mut testing in met BC, for both standard and mut-matched therapy.

 Total (n=48)HR+/Her2- (n=28)Any HER2+ (n=7)TN (n=13)Receptor concordant with primary 100%78%77%# Mutations Median (Range)1 (0-4)1 (0-3)1 (1-2)1 (0-4)014 (29%)10 (36 %)04 (31%)118 (38%)11 (39%)4 (57%)3 (23%)213 (27%)5 (18%)3 (43%)5 (38%)3+3 (6%)2 (7%)01 (8%)Prevalent Mutations (>20%)TP53 (38%), PIK3CA (35%)PIK3CA (50%), TP53 (25%)TP53 (60%), ERBB2amp (86%)TP53 (62%),PIK3CA (23%)Other Alterations (#)ATM (1), KIT (1), PDGFRA (1), PTEN(1), RB1 (1), SMAD4 (1), SMO (1), STK11 (1)AKT1 (1), ATM VUS (1), ERBB2 (1), PTEN (1), SMAD4 VUS (1), SMO VUS (1)ERBB2 (1), STK11(1)EGFR amp (2), KIT amp (1),PDGFRA amp (1), RB1 VUS (1)

Citation Format: Soucier-Ernst D, Colameco C, Troxel AB, Clark C, Shih N, Maxwell KN, Morrissette J, Lieberman D, Feldman M, Goodman N, Bradbury A, Clark A, Domchek S, Fox K, Glick J, Matro J, Nathanson K, Chodosh L, DeMichele A. Mutational spectrum and tumor response in metastatic breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P6-07-05.

Differential expression of the neu transgene in murine mammary tissues

The mammary glands of control FVB and mice with MTV-LTR promoted transgenes were stained using immunohistochemistry to detect neu expression. Neu expression in the terminal end buds of developing mammary glands and during early pregnancy in FVB mice was confirmed by in situ hybridization. Neu was expressed in all tumors from mice with the neu transgene but not in tumors expressing transforming growth factor alpha (TGF alpha) or polyoma virus middle T (PyV-MT). Neu was also expressed sporadically in non-neoplastic mammary cells of transgenic neu mice. However, most mammary cells expressing neu were dysplastic. The differential expression of the neu transgene has important implications for the interpretation of transgenic biology.