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.