Abstract A110: Neighborhood racial and ethnic composition typology and colorectal cancer risk: The multiethnic cohort study

Abstract Background: Studies of African American individuals with colorectal cancer (CRC) have found that living in racially and ethnically segregated neighborhoods associates with worse prognosis and survival, while studies of Hispanic and Asian individuals report mixed findings. Segregated neighborhoods may also influence CRC incidence across racial and ethnic minority groups, possibly through social, environmental, or healthcare-related pathways; however, these associations have not been studied. Therefore, we examined associations between neighborhood racial and ethnic composition typologies and CRC incidence among 187,933 African American, Japanese American, Latino/Hispanic, Native Hawaiian, and White participants in the Multiethnic Cohort (MEC) Study, recruited in 1993-1996 from California (primarily Los Angeles County) and Hawaii. Methods: Segregation typology was based on distribution of racial and ethnic groups across census tracts and linked to participants' geocoded baseline residential addresses. Hazard ratios (HRs) and 95% confidence intervals (CIs) for CRC risk were estimated using multivariable Cox proportional hazards regression with age as the time metric and adjusted for age, sex, family history of CRC, personal polyp history, lifestyle factors, and neighborhood socioeconomic status (nSES). Models for Latino/Hispanic participants were additionally adjusted for nativity. Analyses were stratified by state and self-reported race and ethnicity. For each state and racial and ethnic group, the reference typology was specific to co-ethnic residents. Participants were followed through December 31, 2019. Results: Over a median follow-up of 24 years, 5,635 CRC cases were identified. In California, among Latino/Hispanic participants, residing in mixed Hispanic and Black neighborhoods reduced CRC risk relative to residing in predominantly Hispanic areas (HR=0.69, 95%CI=0.48–0.99). This inverse association was observed for foreign-born Latino/Hispanic participants (HR=0.56, 95%CI=0.35-0.90), and no association was found for U.S. born Latino/Hispanic participants. Additionally, foreign-born Latino/Hispanic participants residing in mixed Hispanic and Asian/Pacific Islander neighborhoods had higher CRC risk (HR=1.42, 95%CI=1.01–2.00) relative to those in predominantly Hispanic areas. No associations were found for other racial and ethnic groups in California or Hawaii. Conclusion: Neighborhood racial and ethnic composition typology was associated with CRC risk among Latino/Hispanic participants in the MEC, independent of individual-level factors and nSES, with differences by nativity. Among foreign-born Latino/Hispanic participants, living in mixed Hispanic and Black neighborhoods reduced risk of disease, while residence in mixed Hispanic and Asian/Pacific Islander neighborhoods increased CRC risk. These findings highlight the importance of neighborhood context in understanding CRC disparities among Latino/Hispanic individuals, particularly those who are foreign-born, and supports future investigation into mechanisms underlying these associations. Citation Format: Catherine P. Walsh, Meera Sangaramoorthy, Song-Yi Park, Joseph Gibbons, Salma Shariff-Marco, S. Lani Park, Gertraud Maskarinec, Anna H. Wu, Christopher A. Haiman, Lynne Wilkens, Loïc Le Marchand, Iona Cheng. Neighborhood racial and ethnic composition typology and colorectal cancer risk: The multiethnic cohort study [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 A110.