Examining the Role of the Social Vulnerability Index in the Association Between Race/Ethnicity with Breast Cancer Outcomes

BACKGROUND: Socioeconomic and environmental inequities may increase vulnerability to breast cancer (BC) among racial and ethnic groups. We examined whether the Social Vulnerability Index (SVI) mediates associations between race/ethnicity and BC outcomes, including late-stage diagnosis and BC-specific mortality. METHODS: We conducted a retrospective analysis of 739,448 BC patients from the SEER 18 registries (2000-2016). Mediation analysis evaluated five 2010 SVI themes-socioeconomic status, household composition, minority status/language, housing/transportation, and overall SVI-in associations between race/ethnicity and BC outcomes among non-Hispanic (NH) Black, NH Asian/Pacific Islander (API), and Hispanic women compared with NH White patients. Percent mediated quantified the proportion of total effects explained by indirect pathways. RESULTS: Among NH Black patients, socioeconomic and overall vulnerability mediated 12.9% and 9.5% of disparities in late-stage diagnosis and mortality, respectively. For API patients, household composition and minority status/language explained 18.5% and 14.7% of mortality differences, with no significant mediation for late-stage diagnosis. Among Hispanic patients, overall vulnerability mediated 9.1% of the disparity in late-stage diagnosis. For BC mortality, socioeconomic, household composition, and overall SVI themes mediated 31.4%, 17.3%, and 30.4% of the 13% higher mortality risk among Hispanic women compared with NH White women. Across NH Black, Hispanic, and Asian women, higher minority status/language vulnerability was associated with ~13% lower BC mortality. CONCLUSIONS: Social vulnerability components partially mediated racial and ethnic disparities in BC stage and mortality. IMPACT: Distinct SVI domains influenced outcomes differently across groups, highlighting the need for structurally focused interventions to improve equity in BC outcomes.