Social determinants and lifestyle factors driving colorectal cancer mortality disparities in younger Black and White patients

Background : Disparities in colorectal cancer (CRC) mortality in Black compared to White patients are more evident at younger ages. Emerging data suggests that earlier age of diagnosis in Blacks is associated with socioeconomic and lifestyle factors such as smoking and alcohol use; however, whether these factors contribute to differences in race- and age-specific CRC mortality remains unclear. Methods : Data from the Medical University of South Carolina (MUSC) Hollings Cancer Center cancer registry was used to identify analytic CRC cases from 2000 - 2021 with ≥12 months of follow-up. This study was approved by the MUSC Institutional Review Board. Cox proportional hazards regression estimated risk of death (HR, [95% CI]) for Black versus White patients adjusting for age, sex, stage, year of diagnosis, and treatment. Interactions assessed were race x age (continuous), race x social deprivation index (SVI, high vs low), race x alcohol use (current vs not), race x smoking (current vs not). Results : Of 1,324 patients, 43.5% were female, and 31.7% Black. Median age 62 years; 60 years for Black, 63 years for White. Median survival of 68 months for Blacks and 95 months for Whites. Blacks had higher adjusted risk of death (1.19 [1.01-1.40] vs Whites). There was significant interaction for race by age (p=0.01): Blacks <65 years had greater mortality than Whites (HR 1.38 [1.10-1.69]), with no racial difference observed for those ≥65 years (HR 0.99 [0.76-1.28]). We observed a significant race by SVI interaction (p=0.04): among those with higher SVI, Black patients had modest decrease in risk of death (HR 0.88 [0.66-1.16]) whereas Whites had an increased risk (HR 1.24 [1.02-1.49]); this difference was confined to those <65 years. A significant race by alcohol interaction was also present (p=0.0001): current drinkers who were Black had an increased risk of death (HR 1.63 [1.20-2.22]), while those who were White had a lower risk (HR 0.82 [0.67-1.00]), again limited to patients <65 years. Current smoking increased risk of death in both Blacks (HR 1.70 [1.23-2.35]) and Whites (HR 1.33 [1.05-1.67]), with no significant race x smoking interaction (p=0.22) or age-specific effect. Ever smoking or ever drinking yielded similar but attenuated results. Mortality risk did not differ by sex. Conclusion : Black CRC patients <65 years had higher mortality risk than Whites, and specifically those with current alcohol use and concurrent smoking/alcohol use. No racial difference observed for those ≥65 years. Younger Black people with higher SVI (more vulnerability) had lower mortality than Whites with similar SVI, suggesting that access to health services in poorer Black communities improves outcomes. These findings identify a particularly vulnerable subpopulation that may benefit from targeted interventions focused on improving care access, addressing social barriers, and enhancing smoking and alcohol screening