Racial and Ethnic Variation in Survival in Early-Onset Colorectal Cancer.

Importance: Rates of early-onset (before 50 years of age) colorectal cancer (EOCRC) are increasing, with notable differences across racial and ethnic groups. Limited data are available on EOCRC-related mortality differences when disaggregating racial and ethnic groups. Objective: To investigate racial and ethnic differences in EOCRC mortality, including disaggregation of Asian American populations separately, including Native Hawaiian or Other Pacific Islander populations and specific Asian American groups, and to quantify the contribution of clinical and sociodemographic factors accounting for these differences. Design, Setting, and Participants: This population-based cohort study included California Cancer Registry data for individuals aged 18 to 49 years with EOCRC between January 1, 2000, to December 31, 2019. Median follow-up was 4.2 (IQR, 1.6-10.0) years. The data analysis was conducted between July 1, 2021, and September 30, 2024. Exposure: Race and ethnicity defined as Asian American (and 7 disaggregated subgroups), Hispanic, Native Hawaiian or Other Pacific Islander, non-Hispanic American Indian or Alaska Native, non-Hispanic Black, and non-Hispanic White. Main Outcomes and Measures: Cox proportional hazards regression models were used to measure association between race and ethnicity and CRC mortality risk, yielding adjusted hazard ratios (AHRs) and 95% CIs. Associations of sociodemographic, health system, and clinical factors with differences in mortality by racial and ethnic minority group were assessed using sequential modeling. Results: There were 22 834 individuals diagnosed with EOCRC between 2000 and 2019 (12 215 [53.5%] male; median age, 44 [IQR, 39-47] years). Racial and ethnic identity included 3544 (15.5%) Asian American, 6889 (30.2%) Hispanic, 135 (0.6%) Native Hawaiian or Other Pacific Islander, 125 (0.5%) non-Hispanic American Indian or Alaska Native, 1668 (7.3%) non-Hispanic Black, and 10 473 (45.9%) non-Hispanic White individuals. Compared with non-Hispanic White individuals, higher EOCRC mortality was found for Native Hawaiian or Other Pacific Islander (AHR, 1.34; 95% CI, 1.01-1.76) and non-Hispanic Black (AHR, 1.18; 95% CI, 1.07-1.29) individuals. Disaggregation of Asian American ethnic groups revealed notable heterogeneity, but no single group had increased EOCRC mortality risk after full adjustment for covariates. For Hispanic individuals, there was higher EOCRC mortality (AHR, 1.15 [95% CI, 1.08-1.22]) with the base model (adjustment for age, sex, and tumor characteristics), but the association disappeared once neighborhood socioeconomic status was added to the base model (AHR, 1.00 [95% CI, 0.94-1.06]). Similarly, there was higher EOCRC mortality among Southeast Asian individuals with the base model (AHR, 1.17 [95% CI, 1.03-1.34], but that association disappeared with the addition of insurance status to the model (AHR, 1.10 [95% CI, 0.96-1.25]). Conclusions and Relevance: In this cohort study, racial and ethnic disparities in EOCRC mortality were evident, with the highest burden among Native Hawaiian or Other Pacific Islander and non-Hispanic Black individuals. These results provide evidence of the role of social determinants of health in explaining these differences.