Racial Disparities in Locoregional Recurrence in Postmenopausal Patients with Stage I–III, Hormone Receptor-Positive Breast Cancer Enrolled in the NSABP B-42 Clinical Trial

Background: There are limited data examining racial disparities in locoregional recurrence (LRR) among women with access to high-quality care. We aimed to examine differences in late LRR by race in patients with stage I–IIIA, hormone receptor-positive (HR+) breast cancer enrolled in the National Surgical Adjuvant Breast and Bowel (NSABP) B-42 trial. Methods: From 2006 to 2010, 3966 postmenopausal women with stage I–IIIA HR+ breast cancer who were disease-free after 5 years of endocrine therapy were randomized to an additional 5 years of endocrine therapy or placebo. Patients were excluded if multi-racial or if race was unknown. Kaplan–Meier curves were used to estimate 6-year LRR from the time of trial registration and according to race. Cox proportional hazards models were used for adjusted survival analyses. Results: Overall, 3929 NSABP B-42 patients were included: 3688 (93.9%) White, 151 (3.8%) Black, and 90 (2.3%) Asian patients. Median follow-up was 75.2 months. Overall estimated 6-year LRR from trial registration was 1.8% and differed by race: LRR rates were 1.7% in White women, 4.9% in Black women, and 0% in Asian women (p = 0.046). Adjusted Cox proportional hazards analysis found Black race to be independently associated with LRR (hazard ratio [HzR] 2.36, 95% confidence interval [CI] 1.01–5.49; p = 0.047). Node-positivity was also associated with increased LRR (HzR 1.75, 95% CI 1.07–2.86; p = 0.025). Adjusted Cox analysis found LRR (HzR 2.32, 95% CI 1.33–4.06; p = 0.003) to be associated with increased overall mortality; however, race was not independently associated with mortality. Conclusion: Among postmenopausal patients with stage I–IIIA HR+ breast cancer in the NSABP B-42 trial, racial differences in late LRR were present, with the highest LRR in Black women.