Abstract 894: Prostate cancer outcomes in Hispanic/Latino ethnic enclaves: Results from the California Cancer Registry and American Community Survey.

Abstract Introduction: Prostate cancer (PCa) is the most commonly diagnosed cancer among Hispanic/Latino (H/L) men and the fourth leading cause of cancer-related death. We and others have shown that nativity influences patterns of PCa treatment and survival among H/L men. Here, we examined whether these associations were modified by residence in H/L ethnic enclaves. Methods: We conducted a retrospective, population-based study of primary PCa cases diagnosed from 2005-2021 in the California Cancer Registry, linked to census tract characteristics from the American Community Survey (2010, 2015, 2020). A composite H/L Enclave Index (HEI) was created using the proportions of H/L residents, non-US-born H/L residents, H/L individuals with limited English proficiency, and linguistically isolated households, with principal components analysis applied to all census tracts to derive the first component. Enclave residence was defined as living in a census tract in the 5th quintile of HEI with ≥ 250 H/L residents or in an adjacent 4th-quintile tract meeting the same threshold. We examined enclave residence as a main exposure in the full cohort and, among H/L patients, as a potential modifier of nativity-outcome associations. Multivariable mixed-effects logistic regression models estimated associations with high-grade disease (Gleason ≥ 8), treatment receipt and treatment delay (≥3 months), including nativity-enclave interaction terms. Prostate-specific survival was evaluated using a covariate-adjusted mixed-effects Weibull model. All models included random intercepts to account for census tract clustering. Results: A total of 249,860 prostate cancer cases were included (29,159 H/L), of which 75,496 (30.2%) had ever resided in an H/L ethnic enclave: 17.1% NHW men, 50.1% US-born and 71.8% of non-US-born H/L men (pairwise p0.01). Living in an H/L ethnic enclave was associated with 4% higher odds of presenting with high-grade disease (OR= 1.04; 95% CI: 1.02-1.07) and 15% higher hazard of mortality (HR= 1.15; 95% CI: 1.08-1.22). Among H/L men living outside enclaves, non-US-born men had lower odds of high-grade disease compared with US-born men (OR=0.90; 95% CI: 0.83, 0.97); however, we found no evidence of effect modification (interaction p = 0.17). Similarly, we found no evidence that enclave residence modified nativity differences in treatment receipt (interaction p = 0.22), treatment delay (interaction p = 0.66), or survival (interaction p = 0.08). Conclusions: Our analyses show that residence in an H/L ethnic enclave is associated with higher risk of high-grade PCa and mortality. Ethnic enclave residence had limited influence on differences in prostate cancer stage, treatment, or survival among H/L patients by nativity. Our findings suggest that neighborhood ethnic composition alone may not drive our previously observed disparities in prostate cancer outcomes by nativity. Citation Format: Diego Alvarez-Lopez, Joel Sanchez Mendez, Michelle Tran, Laura Thompson, Lihua Liu, Myles Cockburn, Mariana C. Stern. Prostate cancer outcomes in Hispanic/Latino ethnic enclaves: Results from the California Cancer Registry and American Community Survey abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 894.