Racial disparities in mortality outcomes among women diagnosed with breast cancer in Maryland: Impact of cardiovascular disease and clinical characteristics

Background: Although racial disparities in breast cancer (BC) mortality have been well documented in the United States, little is known about the impact of coexisting cardiovascular disease (CVD) and other clinical factors on Black-White survival disparities after the diagnosis of BC. This study examined the associations of race, CVD, and clinical factors at diagnosis with the hazard of BC and CVD-related mortality among patients with BC identified from the Maryland Cancer Registry. Methods: A total of 36,088 women (25,181 Whites and 10,907 Blacks) diagnosed with incident invasive BC between 2007 and 2017 were included. Subdistribution hazard ratios (sdHRs) for CVD-related and BC mortality were estimated with Fine and Gray regression models, which accounted for the influence of competing events. Results: After a median follow-up of 5.8 years, 8019 deaths occurred; 3896 were BC deaths, and 1167 deaths were CVD-related. Black women had a higher hazard of BC mortality (sdHR, 1.66; 95% confidence interval [CI], 1.55-1.77) and CVD mortality (sdHR, 1.33; 95% CI, 1.17-1.51) in comparison with White women. Associations with CVD mortality were significantly stronger among Black women aged 50 to 59 years (sdHR, 2.86; 95% CI, 1.84-4.44; P for interaction <.001). Among Black women with CVD, the hazard of BC death was 41% higher in comparison with White women. By treatment, a significant association with CVD mortality was observed only among Black women undergoing surgery and radiation (sdHR, 1.61; 95% CI, 1.22-2.13). Conclusions: Clinicians should consider the impact of younger age, preexisting CVD, and BC treatments among Black patients. Early identification of those at risk for worse survival may improve surveillance and outcomes.