Abstract
BACKGROUND: Women with a lower socioeconomic status (SES) have an increased risk of dying from breast cancer (BC) than those with a higher SES. The association of SES with BC survival may be partially mediated by factors such as Oncotype DX (ODX) testing and stage at diagnosis. This study aims to examine SES disparities in survival among HR+/HER2- BC women and to quantify the mediating effects of the ODX test and stage. METHODS: We used data from the Louisiana Tumor Registry to identify women aged 20-90 years diagnosed with stage I-II in 2011-2014 and stage I-III in 2015-2017 HR+/HER2- BC who underwent BC surgery. The follow-up cutoff date was 31 December 2020. Cox proportional hazard regression and generalized mediation analysis were both performed. RESULTS: Of 8931 BC women, 41.4% underwent ODX testing. After adjusting for sociodemographic, tumor characteristic, and treatment variables, low SES women had a higher hazard of overall death (HR = 1.16, 95% CI: 1.02-1.32) and BC-specific death (HR = 1.37; 95% CI: 1.01-1.87) compared to high SES women. The ODX test and stage explained 9.0% and 11.2% SES differences in the hazard of overall death and 4.4% and 13.3% in BC-specific death, respectively. CONCLUSIONS: Low SES is associated with higher hazard rates of overall and cause-specific death among women with breast cancer, even after adjustment. Differences in Oncotype DX (ODX) testing and stage at diagnosis explained part of these disparities. Targeted interventions are needed to improve access to genomic testing and early detection to reduce SES-related disparities in breast cancer outcomes.