Abstract P3-11-02: Breast cancer-specific mortality (BCSM) in patients (pts) with node-negative (N0) and node-positive (N+) breast cancer (BC) guided by the 21-gene assay: A SEER-genomic population-based study

Abstract

Introduction: The 21-gene Breast Recurrence Score® (RS) in the randomized NSABP B-20, SWOG S8814, and TAILORx studies predicted chemotherapy (CT) benefit for pts with N0 and N+ disease. Endocrine therapy was not inferior to chemoendocrine therapy in 6,711 randomized TAILORx pts with RS 11-25 and N0 disease. We characterized BCSM for the TAILORx-defined RS groups (0-10, 11-15, 16-20, 21-25, and 26-100) in the large population-based SEER study of pts treated based on RS results. Methods: RS results were provided electronically to SEER registries per their linkage methods (Petkov npj Breast Cancer 2016). Eligible pts were diagnosed Jan 2004 - Dec 2014 with N0 and N+(N1mic, 1-3 positive nodes[N1]), HR+, HER2-negative BC, and had no prior malignancy or multiple tumors, with follow-up information through Dec 2015. BCSM estimates by reported CT use yes vs. no/unknown were computed, and must be interpreted cautiously given lack of randomization. Results: There were 80,605 pts with RS results; 70,087 with N0 disease, 4,336 with N1mic, and 6,182 with N1. Median follow-up was 49 months, with 20,151 pts followed >76 months. 1,020 pts had experienced breast cancer death. There was a significant positive association between higher RS results and increased BCSM (p Conclusion: In both N0 and N+ disease (up to 3 positive nodes), low RS results identify more than 70% of BC patients with excellent long-term outcomes and no apparent CT benefit, and high RS results (26-100) identifies an important minority of patients where CT reduces BCSM. Real-world evidence from SEER reconfirms that the 21-gene assay is prognostic and strongly suggests it is predictive of CT benefit, irrespective of nodal status. Citation Format: Hortobagyi GN, Shak S, Sledge, Jr. GW, Winer EP, Albain KS, Mamounas EP, Jakubowski DM, Petkov VI, Wolmark N. Breast cancer-specific mortality (BCSM) in patients (pts) with node-negative (N0) and node-positive (N+) breast cancer (BC) guided by the 21-gene assay: A SEER-genomic population-based study [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 P3-11-02.