Factors That Contributed to Black-White Disparities in Survival Among Nonelderly Women With Breast Cancer Between 2004 and 2013

Abstract

Purpose To estimate the contribution of differences in demographics, comorbidity, insurance, tumor characteristics, and treatment to the overall mortality disparity between nonelderly black and white women diagnosed with early-stage breast cancer. Patients and Methods Excess relative risk of all-cause death in black versus white women diagnosed with stage I to III breast cancer, expressed as a percentage and stratified by hormone receptor status for each variable (demographics, comorbidity, insurance, tumor characteristics, and treatment) in sequentially, propensity-scored, optimally matched patients by using multivariable hazard ratios (HRs). Results We identified 563,497 white and black women 18 to 64 years of age diagnosed with stage I to III breast cancer from 2004 to 2013 in the National Cancer Data Base. Among women with hormone receptor-positive disease, who represented 78.5% of all patients, the HR for death in black versus white women in the demographics-matched model was 2.05 (95% CI, 1.94 to 2.17). The HR decreased to 1.93 (95% CI, 1.83 to 2.04), 1.54 (95% CI, 1.47 to 1.62), 1.30 (95% CI, 1.24 to 1.36), and 1.25 (95% CI, 1.19 to 1.31) when sequentially matched for comorbidity, insurance, tumor characteristics, and treatment, respectively. These factors combined accounted for 76.3% of the total excess risk of death in black patients; insurance accounted for 37.0% of the total excess, followed by tumor characteristics (23.2%), comorbidities (11.3%), and treatment (4.8%). Results generally were similar among women with hormone receptor-negative disease, although the HRs were substantially smaller. Conclusion Matching by insurance explained one third of the excess risk of death among nonelderly black versus white women diagnosed with early-stage breast cancer; matching by tumor characteristics explained approximately one fifth of the excess risk. Efforts to focus on equalization of access to care could substantially reduce ethnic/racial disparities in overall survival among nonelderly women diagnosed with breast cancer.