Abstract Introduction: Colorectal cancer (CRC) is the second most common cancer among Hispanic/Latino (H/L) individuals in California. We previously showed that nativity and individual-level factors impact tumor localization, treatment patterns, and survival. To understand our findings further we considered the role of ethnic enclave residence. Methods: California census tract-level data from the American Community Survey (2010, 2015, 2020, 5-year estimates) were used to construct a composite H/L ethnic enclave indicator based on validated methods. The composite considered the percentage of H/L individuals, non-US born H/L individuals, H/L with limited English proficiency, and linguistically isolated households. After principal components analyses, a dichotomous indicator (ever vs. never resided in an H/L enclave) was constructed and linked to California Cancer Registry cases of primary invasive CRC diagnosed between 2005 and 2021 at least 18 years old. H/L cases were stratified by nativity status (US-born vs. non-US-born). Multivariable mixed-effects logistic regression models were fitted to assess tumor site (colon vs. rectum), treatment receipt (no vs. yes), and time to treatment (3 months vs. = 3 months). A covariate-adjusted mixed-effects parametric survival model with a Weibull distribution was used to evaluate CRC-specific survival. All models included a random intercept to account for census tract clustering. Results: A total of 1591, 1594, and 1805 census tracts (out of a total of 9042 tracts), were classified as ethnic enclaves in 2010, 2015, and 2020, respectively, with 49% of the tracts remaining an enclave throughout the study period. These tracts were matched to 186,214 CRC cases (73.9% Non-Hispanic White (NHW), 9.44% Non-Hispanic Black, 7.14% US-born H/L, and 9.6% non-US-born H/L). While only 12% of NHW individuals had ever lived in an H/L enclave, 30% of US-born and 47% of non-US-born H/L individuals had resided in enclaves (pairwise p-values 0.001). We found no evidence of effect modification by ethnic enclave residence when H/L cases were compared to NHW individuals. Within the H/L population, and relative to US-born H/L who had never lived in an enclave, non-US-born H/L individuals in enclaves were more likely to have rectal tumors (OR = 1.14; 95% CI: 1.07-1.22), and to not receive treatment (OR = 0.84; 95% CI: 0.71-0.99). Moreover, US-born H/L cases in enclaves, and non-US-born H/L in and outside of enclaves were 1.26 (95% CI: 1.02-1.56), 1.19 (95% CI: 1.01-1.40) and 1.47 (95% CI: 1.23-1.80) times as likely to have to wait = 3 months to receive treatment. Non-US-born H/L individuals had better CRC-specific survival than their US-born counterparts. However, the association was not modified by enclave residence (p-interaction = 0.991). Conclusion: Our findings suggest that the built and social environment of H/L CRC patients living in California may exacerbate underlying disparities in relation to tumor location, time to treatment and treatment receipt among non-US born H/L patients. Citation Format: Joel Sanchez Mendez, Diego Alvarez Lopez, Michelle Tran, Laura Thompson, Lihua Liu, Myles Cockburn, Mariana C. Stern. The role of residence in ethnic enclaves on colorectal cancer tumor characteristics, treatment patterns, and cancer outcomes among Hispanic/Latino patients: Results from the California Cancer Registry and American Community Survey abstract. In: Proceedings of the 18th AACR Conference on the Science of Cancer Health Disparities; 2025 Sep 18-21; Baltimore, MD. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2025;34(9 Suppl):Abstract nr A108.
Mendez et al. (Thu,) studied this question.