Abstract GS1-01: Race and clinical outcomes in the RxPONDER Trial (SWOG S1007)
Authors: Abdou Yara , Barlow William E. , Gralow Julie R. , Meric-Bernstam Funda , Albain Kathy S. , Hayes Daniel F. , Lin Nancy U. , Perez Edith A. , Goldstein Lori J. , Chia Stephen K. , Dhesy-Thind Sukhbinder , Rastogi Priya , Alba Emilio , Delaloge Suzette , Schott Anne F. , Shak Steven , Sharma Priyanka , Lew Danika L. , Miao Jieling , Unger Joseph M. , Tripathy Debu , Pusztai Lajos , Hortobagyi Gabriel N. , Kalinsky Kevin 
Published: March 2023

Abstract
Introduction: Racial disparities in breast cancer (BC) outcomes continues to be a major health care challenge. The 21-gene recurrence score (RS) is an important tool to guide treatment (tx) decisions among women with early-stage BC. We report an analysis of clinical characteristics, survival outcomes and race in association with RS in participants (pts) in the RxPONDER trial.
Methods: We analyzed clinical outcomes with respect to race and ethnicity. Unreported race excluded 18.7% of the pts, with most due to privacy rules. The primary outcome was invasive disease-free survival (IDFS). Distant relapse-free survival (DRFS) was also evaluated. Analyses adjusted for assigned tx arm, RS, and grade were performed. There were too few events to include Native American/Pacific Islander (NAPI) women in the survival analyses.
Results: A total of 4,048 trial women with Hormone Receptor positive, HER2 negative (HR+/HER2-) BC, 1-3 involved axillary lymph nodes (LNs), RS ≤ 25 and known race/ethnicity were included in this analysis including the following: 2,833 non-Hispanic (NH) White pts (70%), 248 NH Black pts (6.1%), 610 Hispanic pts (15.1%), 324 Asian pts (8.0%), and 33 NAPI pts (0.8%). Asian and Hispanic women were younger than NH Whites (by 7.1 and 2.4 years, respectively) but NH Blacks did not differ in age. RS distribution did not differ among all racial subgroups (p=0.49). There were also no significant differences in tumor size (p=0.10) or number of positive LNs (p=0.26) across all racial groups. However, tumor grade was found to be significantly different with grade 3 tumors higher for NH Blacks (18.0%), NH NAPI (21.1%), and Hispanics (14.5%) vs. NH Whites (10.4%) and Asians (6.5%) (p&lt; 0.001). Overall five-year IDFS was lower for NH Blacks (87.0%) compared to that for Asians (93.9%), NH Whites (91.5%), and Hispanics (91.4%) (Table 1). A multivariable Cox model adjusting for RS and tx arm showed worse IDFS for NH Blacks compared to NH Whites (HR=1.38; 95% CI 1.00-1.90; p=0.048), although Asian pts had better IDFS than NH Whites (HR=0.65; 95% CI 0.44-0.97; p=0.034). In a separate analysis by menopausal status the magnitude of the IDFS hazard ratios (HRs) for NH Blacks was similar, although no longer statistically significant (premenopausal HR=1.37; 95% CI 0.69-2.72; postmenopausal HR=1.38; 95% CI 0.96-1.98). While there was no statistically significant interaction between NH Blacks vs. NH Whites and tx arm for either premenopausal (p=0.99) or postmenopausal women (p=0.44), adjusting for RS, the small number of events in the NH Black cohort, particularly in premenopausal women (n = 9 IDFS events), limit power and inference about differences in chemotherapy benefit. Among postmenopausal women, NH Blacks had worse DRFS compared to NH Whites (HR=1.69; 95% CI 1.12-2.53; p=0.01), adjusting for tx and RS. A similar trend was seen among premenopausal women (HR=1.74; 95% CI 0.79-3.82; p=0.17), although not statistically significant. Data on tx adherence over 5 years was not mature, although NH Blacks were more likely to accept tx assignment compared to NH Whites at randomization (93% vs. 86%, p=0.004).
Conclusion: Black women with HR+/HER2- BC, 1-3 involved LNs and RS ≤ 25 have worse outcomes compared to White women despite similar RS results. There was no significant interaction between NH Blacks vs. NH Whites and tx arm, although this analysis was limited due to sample size. There remains an important need for novel approaches to improve clinical outcomes particularly for NH Black Women.
Table 1. IDFS by Race and Ethnicity.
Citation Format: Yara Abdou, William E. Barlow, Julie R. Gralow, Funda Meric-Bernstam, Kathy S. Albain, Daniel F. Hayes, Nancy U. Lin, Edith A. Perez, Lori J. Goldstein, Stephen K. Chia, Sukhbinder Dhesy-Thind, Priya Rastogi, Emilio Alba, Suzette Delaloge, Anne F. Schott, Steven Shak, Priyanka Sharma, Danika L. Lew, Jieling Miao, Joseph M. Unger, Debu Tripathy, Lajos Pusztai, Gabriel N. Hortobagyi, Kevin Kalinsky. Race and clinical outcomes in the RxPONDER Trial (SWOG S1007) [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 GS1-01.