Age, Body Mass Index, Tumor Subtype, and Racial and Ethnic Disparities in Breast Cancer Survival.

IMPORTANCE: Black women in the United States have higher breast cancer (BC) mortality rates than White women. The combined role of multiple factors, including body mass index (BMI), age, and tumor subtype, remains unclear.

OBJECTIVE: To assess the association of race and ethnicity with survival among clinical trial participants with early-stage BC (eBC) according to tumor subtype, age, and BMI.

DESIGN, SETTING, AND PARTICIPANTS: This cohort study analyzed survival data, as of November 12, 2021, from participants enrolled between 1997 and 2010 in 4 randomized adjuvant chemotherapy trials: Cancer and Leukemia Group B (CALGB) 9741, 49907, and 40101 as well as North Central Cancer Treatment Group (NCCTG) N9831, legacy groups of the Alliance of Clinical Trials in Oncology. Median follow-up was 9.8 years.

EXPOSURES: Non-Hispanic Black and Hispanic participants were compared with non-Hispanic White participants within subgroups of subtype (hormone receptor positive [HR+]/ERBB2 [formerly HER2] negative [ERBB2-], ERBB2+, and HR-/ERBB2-), age (<50, 50 to <65, and ≥65 years), and BMI (<18.5, 18.5 to <25.0, 25.0 to <30.0, and ≥30.0).

MAIN OUTCOMES AND MEASURES: Recurrence-free survival (RFS) and overall survival (OS).

RESULTS: Of 9479 participants, 436 (4.4%) were Hispanic, 871 (8.8%) non-Hispanic Black, and 7889 (79.5%) non-Hispanic White. The median (range) age was 52 (19.0-89.7) years. Among participants with HR+/ERBB2- tumors, non-Hispanic Black individuals had worse RFS (hazard ratio [HR], 1.49; 95% CI, 1.04-2.12; 5-year RFS, 88.5% vs 93.2%) than non-Hispanic White individuals, although the global test for association of race and ethnicity with RFS was not significant within any tumor subtype. There were no OS differences by race and ethnicity in any subtype. Race and ethnicity were associated with OS in young participants (age <50 years; global P = .008); young non-Hispanic Black participants (HR, 1.34; 95% CI, 1.04-1.71; 5-year OS, 86.6% vs 92.0%) and Hispanic participants (HR, 1.62; 95% CI, 1.16-2.29; 5-year OS, 86.2% vs 92.0%) had worse OS than young non-Hispanic White participants. Race and ethnicity were associated with RFS in participants with BMIs of 25 to less than 30, with non-Hispanic Black participants having worse RFS (HR, 1.81; 95% CI, 1.23-2.68; 5-year RFS, 83.2% vs 87.3%) than non-Hispanic White participants.

CONCLUSIONS AND RELEVANCE: In this cohort study, racial and ethnic survival disparities were identified in patients with eBC receiving standardized initial care, and potentially at-risk subgroups, for whom focused interventions may improve outcomes, were found.