Racial differences in breast cancer-specific mortality and CVD-specific mortality after breast cancer in post-menopausal women

Background: Racial disparities in all-cause mortality after breast cancer (BC) have been documented. While elevated risk of BC mortality experienced by Black women is clear, it is unclear the relative contribution of cardiovascular disease (CVD) mortality to the survival disparity in Black women. Methods: This analysis from the Women’s Health Initiative (WHI) included 8,410 women diagnosed with invasive BC during follow-up. Cardiovascular (CV) events were defined as adjudicated myocardial infarction, heart failure, or stroke. Cause of death was determined through adjudication by medical chart review, ICD codes, death certificate, and/or autopsy report. 10-year cumulative incidence rates were calculated for CV events, CVD mortality, and BC mortality, stratified by race. Sub-distribution hazards ratios (sHR) were calculated using Fine and Gray models to account for competing risks. Results: In BC survivors (mean age = 70.9 years, median follow-up = 15.1 years), 8.5% self-reported as Black. Compared to White women, Black women had higher 10-year cumulative incidence of non-fatal CV events (10.9% vs. 8.2%, P = 0.001) and BC mortality (15.3% vs. 11.5%, P = 0.039). In contrast, White women had higher 10-year incidence of CVD mortality (7.2% vs. 10.1%, P = 0.001). BC mortality in Black women represented a higher proportion of death (35% vs. 20%), which was not true for White women. Conclusion: Our study reinforces prior findings that racial disparities are experienced by Black women with BC. This may be in large part driven by BC mortality. However, if improvements in BC mortality are made to reduce this gap, disparities in CVD mortality may become more prominent due to racial disparities in CV events.