Abstract C113: Mediation of race/ethnicity disparities in physical patient reported outcomes (PROS) by socioeconomic position, comorbidities, and tumor biology among elderly female breast cancer (BC) patients in the SEER-MHOS database

Objective: Variations in physical PROs between Non-Hispanic Black (NHB) and Hispanic compared to Non-Hispanic White (NHW) elderly women with BC may be attributable to differences in socioeconomic position (SEP), comorbidities, and tumor biology (TB). We examine the extent to which the race/ethnicity disparity in patient reported physical component score (PCS) is transmitted through these domains. Methods: Data is from the Surveillance, Epidemiology, and End Results- Medicare Health Outcomes Survey dataset (SEER-MHOS) which is used to research health outcomes in cancer patients. The analytic sample (n=19,857) included 14,936 NHW, 2,897 NHB, and 2,024 Hispanic women with newly diagnosed BC between 2010-2017. PCS were calculated using the SF-36/V linear transformation of 0-100 versions of the scale that yield a population mean of 50 and standard deviation of 10 based on 1990 population means. We estimated average controlled direct associations (ACDA) using regression models with predictive margins to evaluate crude and age/body mass index (BMI)-adjusted PCS by race/ethnicity and performed a series of ACDA [with comparison of rescaled coefficients (RC)] controlling for the domains of SEP [household income (< 30K, 30K-80K, >80K) and education attainment [HS)], comorbidities [smoking status (current smoker/current non-smoker), diabetic (yes/no), and hypertensive (yes/no)], and tumor biology [stage(1-3), grade (well/moderate/poor), and subtype (luminal A/triple negative)]. Results: Overall, NHB and Hispanic women were younger and had a higher BMI than NHW women. In baseline age/BMI adjusted models, NHWs had PCSs 3.4 points significantly higher than both NHWs and Hispanics (95% CI: 2.8, 3.9 and 2.8, 4.1, respectively). Adjusting for SEP reduced the observed disparity: NHB (1.6; 95% CI: 0.90, 2.3) and Hispanics (0.76; 95% CI: 0.04, 1.6) compared to NHW. Inclusion of all three domains highly attenuated the observed PCS disparities between the minority populations and NHWs (0.20; 95%CI: -1.1, 1.5) for NHB and (0.54; 95%CI: -0.90, 1.99) for Hispanics compared to NHWs]. Based on the method of RC, we determined the SEP accounted for the largest fraction of mediated effects, followed by comorbidities, with TB having the smallest effect. Conclusion: Our findings support the hypothesis that observed racial/ethnicity differences in physical PROs in elderly BC patients are largely mediated by differences in SEP and comorbidity, rather than TB. Citatio