Abstract S4-04: Tumor microenvironment of metastasis (TMEM) score is associated with early distant recurrence in hormone receptor (HR) positive, HER2-negative early stage breast cancer (ESBC)

Background: Metastasis is the primary cause of death in ESBC. We have shown in mouse models that a subpopulation of tumor cells expressing invasive Mena isoforms stream, form microanatomic structures (“TMEM”) with endothelial cells and macrophages, intravasate into the circulation at TMEM sites, and metastasize (Harney et al. Cancer Discovery, 2015). Further, TMEM sites (“MetaSites”) are identifiable in human ESBC, and “MetaSite score” [MS] is positively associated with distant recurrence in HR+/HER2- ESBC independent of clinicopathologic features, including IHC4 (Rohan et al. JNCI 2014). Here we determined the association between MS and recurrence in an independent ESBC cohort (E2197; NCT00003519). Methods: We evaluated primary tumors from 600 patients (median followup 14.8 years) with ESBC (weighted % = 50% T1, 54% N0, 46% N1) treated with surgery and 4 cycles of adjuvant chemotherapy (AC or AT) and endocrine therapy. Grade, ER, PR, and HER2, and Oncotype DX Recurrence Score (RS) were evaluated in central labs (Badve et al. JCO 2008), and MS was determined in a CLIA-certified lab using an analytically validated, fully automated digital pathology/image analysis method that identifies Mena expressing tumor cells in direct contact with CD68+ macrophages and CD31+ endothelial cells (ie, “TMEMs”, or “MetaSites”). The objectives were to determine the association between MS and distant relapse free interval (DRFI) and relapse free interval (RFI). Kaplan-Meier survival curves were used to estimate time-to-event distributions. Cox proportional hazards models were used to assess hazard ratio associated with MS while controlling for covariates, and allowing time-varying association with MS. Both Kaplan-Meier and Cox regression methods addressed stratified sampling by incorporating proper weights. All analyses were performed in R 3.2.3. Results: MS ranged from 0-199; the weighted mean MS was lower in HR+/HER2- than TN (16.1 vs. 23.8, p=0.001) and HER2+ disease (26.2, p=0.003). MS was not associated with T or N status, and correlated poorly with RS (r=0.29). Proportional hazards models revealed a significant positive association between continuous MS and DRFI (p=0.001) and RFI (p=0.00006) in HR+/HER2- disease in years 0-5 (and by MS tertiles for DRFI [p=0.04] and RFI [p=0.01]), but not after year 5 or in TN or HER2+ disease. Proportional hazards models including clinical covariates (N0 vs. N1; T1 vs. T2; high vs. int. vs. low grade) also revealed significant positive associations for continuous MS with RFI (p=0.04), and borderline association with DRFI (p=0.08). Similar findings for MS (RFI p=0.05;DRFI p=0.10) were noted in a joint model including categorical RS (30). Conclusions: MS, a novel metastasis biomarker reflecting interaction between streaming and metastasizing tumor cells and microenvironment, provides prognostic information complementary to classical clinicopathologic features and RS in HR+/HER2- ESBC. Further evaluation is warranted in order to identify patients at highest risk of recurrence within 5 years most likely to benefit from adjuvant chemotherapy or novel therapies. (Supported by BCRF and NCI CA21115, CA180794, CA23318, CA66636, CA180820). Citation Format: Sparano JA, Gray R, Oktay MH, Entenberg D, Rohan T, Xue X, Donovan M, Peterson M, Shuber A, Hamilton D, D'Alfonso T, Goldstein LJ, Gerlter F, Davidson N, Condeelis J, Jones J. Tumor microenvironment of metastasis (TMEM) score is associated with early distant recurrence in hormone receptor (HR) positive, HER2-negative early stage breast cancer (ESBC) [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 S4-04.