Abstract 3603: Racial and ethnic disparities in colorectal cancer-specific mortality: The Multiethnic Cohort

Abstract Background: Colorectal cancer (CRC) is a leading cause of cancer-related mortality in the United States. However, few studies have investigated the racial and ethnic disparities of CRC-specific mortality in multiethnic populations of adults with CRC while accounting for detailed individual- and neighborhood-level data. Methods: We evaluated racial and ethnic disparities in CRC-specific mortality among 5, 738 (2, 911 men, 2, 827 women) invasive colorectal adenocarcinoma cases (1993-2019) from the Multiethnic Cohort Study (MEC). Cases included African American (n=1, 166), Latino (n=1, 178), Native Hawaiian (N=358), Japanese American (n=1, 960), and non-Hispanic White (NHW) (n=1, 178) adults. Using Cox regression with age since diagnosis as the time metric, we estimated hazard ratios (HRs) for CRC-specific mortality, adjusting for sex, CRC grade/stage, treatment (surgery, chemotherapy, radiotherapy), family history of CRC, history of polyps, education, neighborhood SES (accounting for census block group), BMI, smoking, alcohol, physical activity, diabetes, NSAID and multivitamin use, daily calories, intake of red/processed meats, folate, fiber, and number of comorbidities (0, 1, ≥2). Stratified analyses were performed by sex, tumor stage, and site (colon, left colon, right colon, rectum). Results: Over a mean follow-up period of 7.5 years, 1, 695 (29.5%) CRC cases (874 men and 821 women) died of colorectal adenocarcinoma. Compared to NHW CRC cases, Japanese American (HR=0.74, 95% CI: 0.61, 0.89) and Latino (HR=0.65, 95% CI: 0.51, 0.82) cases had significantly lower CRC-specific mortality. These associations were significant in men (Japanese American: HR=0.74, p=0.02; Latino: HR=0.62, p<0.001), but not in women (HRs = 0.72-0.77, p<0.10). Across stage, Japanese American cases had 36% lower CRC-specific mortality for localized tumors (HR=0.64, 95% CI: 0.43-0.97), while Latino cases had >50% reduced mortality for distant tumors (HR=0.46, 95% CI: 0.31-0.69). For colon cancer specifically, both groups showed significant lower CRC-specific mortality (Japanese American: HR=0.67, 95% CI: 0.41-0.77; Latino: HR=0.65, 95% CI: 0.50-0.85). Results were similar by colon tumor site but were stronger for Japanese American cases for left-sided colon cancer (HR =0.57, 95% CI:0.41-0.77), and for Latino cases for right-sided colon cancer (HR =0.57, 95% CI: 0.41-0.80). There were no significant differences in CRC-specific mortality among African American or Native Hawaiian cases compared to NHWs overall and by subgroups. Conclusions: Japanese American and Latino CRC cases had significantly lower CRC-specific mortality compared to NHWs in the MEC adjusting for prognostic factors. These findings were consistent across CRC stage, tumor site, and among males. Further research is needed to explore the structural, social and biological factors underlying these disparities in CRC-specific mortality. Citation Format: Wei (Melody) Xiong, Adelynn Paik, Iona Cheng, Anna H. Wu, Ugonna Ihenacho, Lynne R. Wilkens, Loïc Le Marchand, David V. Conti, Christopher A. Haiman, Brian Z. Huang. Racial and ethnic disparities in colorectal cancer-specific mortality: The Multiethnic Cohort [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 3603.