Neighborhood social vulnerability and chemotherapy response in breast cancer patients.

e23083 Background: Sociodemographic disparities are a well-known influence on oncologic outcomes, however their relationship to treatment response remains incompletely characterized. Evaluating neighborhood-level social vulnerability as it relates to standard cytotoxic chemotherapy response offers an opportunity to better understand and address disparities in cancer care. We sought to assess the impact of Social Vulnerability Index (SVI) on response to standard of care cytotoxic chemotherapy in breast cancer patients. Methods: We conducted a retrospective cohort study of 180 breast cancer patients treated with cytotoxic chemotherapy at a safety-net academic center. Patients with stage I–IV disease who received chemotherapy in the neoadjuvant or adjuvant setting with curative intent were included. Neighborhood-level social vulnerability was assigned using the Center for Disease Control SVI, based on zip code of residence at diagnosis. Outcomes were analyzed within 5 years of diagnosis and categorized as alive without documented disease progression, disease progression or recurrence on surveillance imaging, or death. Ordinal logistic regression was used to evaluate the association between SVI and chemotherapy response, adjusting for clinical stage and age at diagnosis. Results: Among the 180 patients, 25% resided in low-SVI zip codes, 28% in low-medium, 31% in medium-high, and 17% in high-SVI zip codes. At 5 years, 61% of patients were alive without documented progression, 22% experienced disease progression, and 17% died. Increasing SVI was directionally associated with worse 5-year outcomes, with higher odds of progression or death per one-category increase in SVI (OR 1.36, 95% CI 0.45–4.08; p = 0.589), consistent with higher observed rates of progression or death in higher SVI categories. The direction of association was consistent across alternative SVI categorizations. Conclusions: In our cohort, higher neighborhood-level social vulnerability trended toward worse 5-year outcomes following cytotoxic chemotherapy among breast cancer patients. Findings were limited by sample size and were not statistically significant, but the consistent directional association supports further study. These results suggest that social vulnerability may meaningfully influence long-term chemotherapy response, highlighting the need for larger studies to inform targeted interventions aimed at mitigating disparities in cancer care.