Racial and Socioeconomic Disparities in Breast Cancer Outcomes within the AJCC Pathologic Prognostic Staging System

Background: Non-Hispanic black (NHB) women and those of lower socioeconomic status (SES) have inferior breast cancer outcomes compared with non-Hispanic white (NHW) women and those of higher SES. We examined racial and SES disparities in breast cancer survival within the AJCC 8th edition pathologic prognostic staging system. Methods: Using the Surveillance, Epidemiology and End Results Program, we identified patients diagnosed with invasive breast cancer from 2010 to 2015, with follow-up through 2016. Census tract-level SES (cSES) data were available as a composite index and analyzed in quintiles. Cox proportional-hazards survival analyses adjusted for age, race, cSES, insurance, marital status, histology, pathologic prognostic stage, and treatment were used to estimate disease-specific survival (DSS). Results: A total of 259,852 patients were included: 176,369 (67.9%) NHW; 28,510 (11.0%) NHB; 29,737 (11.4%) Hispanic; and 22,887 (8.8%) Asian. NHB race and lower cSES were associated with increased incidence of triple-negative disease compared with NHW (p < 0.01). NHB race, lower cSES, public insurance, lower education, and increased poverty were associated with lower DSS. Survival analyses adjusting for cSES, tumor, and treatment characteristics demonstrated that NHB patients had inferior DSS within each AJCC pathologic prognostic stage (hazard ratio [HR] 1.25, 95% confidence interval [CI] 1.20–1.30) compared with NHW patients. Fully adjusted models also showed patients residing in lower SES counties had inferior DSS. Conclusions: Racial and cSES disparities in breast cancer-specific mortality were evident across all stages, even within the pathologic prognostic staging system which incorporates tumor biology. Future efforts should assess the biological, behavioral, social, and environmental determinants that underlie racial and SES inequities in outcomes.