Racial disparities in colorectal cancer survival: to what extent are racial disparities explained by differences in treatment, tumor characteristics, or hospital characteristics?

BACKGROUND: Racial/ethnic differences in colorectal cancer (CRC) survival have been documented throughout the literature. However, the reasons for these disparities are difficult to decipher. The objective of this analysis was to determine the extent to which racial/ethnic disparities in survival are explained by differences in sociodemographics, tumor characteristics, diagnosis, treatment, and hospital characteristics.

METHODS: A cohort of 37,769 Medicare beneficiaries who were diagnosed with American Joint Committee on Cancer stages I, II, and III CRC from 1992 to 2002 and resided in 16 Surveillance, Epidemiology, and End Results (SEER) regions of the United States was identified in the SEER-Medicare linked database. Survival was estimated using the Kaplan-Meier method. Cox proportional hazards modeling was used to estimate hazard ratios (HRs) of mortality and 95% confidence intervals (CIs).

RESULTS: Black patients had worse CRC-specific survival than white patients, but the difference was reduced after adjustment (adjusted HR [aHR], 1.24; 95% CI, 1.14-1.35). Asian patients had better survival than white patients after adjusting for covariates (aHR, 0.80; 95% CI, 0.70-0.92) for stages I, II, and III CRC. Relative to Asians, blacks and whites had worse survival after adjustment (blacks: aHR, 1.56; 95% CI, 1.33-1.82; whites: aHR, 1.26; 95% CI, 1.10-1.44). Comorbidities and socioeconomic Status were associated with a reduction in the mortality difference between blacks and whites and blacks and Asians.

CONCLUSIONS: Comorbidities and SES appeared to be more important factors contributing to poorer survival among black patients relative to white and Asian patients. However, racial/ethnic differences in CRC survival were not fully explained by differences in several factors. Future research should further examine the role of quality of care and the benefits of treatment and post-treatment surveillance in survival disparities.