County-level geographic disparities in cardiovascular disease mortality among US breast cancer survivors, 2000-2018.

BACKGROUND: Disparities in cardiovascular disease mortality among breast cancer survivors are documented, but geographic factors by county-level socioeconomic status (SES) and rurality are not well described. METHODS: We analyzed 724 518 women diagnosed with localized or regional stage breast cancer between 2000 and 2017 within Surveillance, Epidemiology, and End Results Program-18 with follow-up until 2018. We calculated relative risks (RRs) of cardiovascular disease mortality using Poisson regression, accounting for age- and race-specific rates in the general population, according to county-level quintiles of SES (measured by Yost index), median income, and rurality at breast cancer diagnosis. We also calculated 10-year cumulative mortality risk of cardiovascular disease accounting for competing risks. RESULTS: Cardiovascular disease mortality was 41% higher among breast cancer survivors living in the lowest SES (RR = 1.41, 95% confidence interval [CI] = 1.36 to 1.46, Ptrend < .001) and poorest (RR = 1.41, 95% CI = 1.36 to 1.47, Ptrend < .001) counties compared with the highest SES and wealthiest counties, and 24% higher for most rural relative to most urban counties (RR = 1.24, 95% CI = 1.17 to 1.30, Ptrend < .001). Disparities for the lowest SES relative to highest SES counties were greatest among younger women aged 18-49 years (RR = 2.32, 95% CI = 1.90 to 2.83) and aged 50-59 years (RR = 2.01, 95% CI = 1.77 to 2.28) and within the first 5 years of breast cancer diagnosis (RR = 1.53, 95% CI = 1.44 to 1.64). In absolute terms, however, disparities were widest for women aged 60+ years, with approximately 2% higher 10-year cumulative cardiovascular disease mortality risk in the poorest compared with wealthiest counties. CONCLUSIONS: Geographic factors at breast cancer diagnosis were associated with increased cardiovascular disease mortality risk. Studies with individual- and county-level information are needed to inform public health interventions and reduce disparities among breast cancer survivors