Racial Disparities in Colorectal Cancer Survival: To What Extent Are Racial Disparities Explained by Differences in Treatment, Tumor 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 to what extent racial/ethnic disparities in survival are explained by differences in socio-demographic, tumor characteristics, diagnosis, treatment and hospital characteristics.

METHODS: A cohort of 37,769 Medicare beneficiaries diagnosed with American Joint Committee on Cancer (AJCC) stages I-III CRC from 1992 to 2002 and residing 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 hazard modeling was used to estimate hazard ratios (HR) of mortality and 95% confidence intervals (95% CI).

RESULTS: Blacks had worse CRC-specific survival than Whites but this was reduced after adjustment (aHR=1.24; 95%CI:1.14-1.35). Asians had better survival than Whites after adjusting for covariates (aHR=0.80; 95%CI: 0.70-0.92) for stages I-III CRC. Relative to Asians, Blacks and Whites had worse survival after adjustment (aHR=1.55; 95% CI:1.33-1.81; aHR=1.25; 95%CI:1.09-1.43, respectively). Comorbidities and SES were associated with a reduction in the mortality difference between Blacks and Whites and Blacks and Asians.

CONCLUSION: Racial/ethnic differences in CRC survival were not fully explained by differences in a number of factors. Comorbidities and SES appear to be more important factors contributing to Blacks' poorer survival relative to Whites and Asians. Future research should further examine the role of quality of care, the benefit of treatment and post-treatment surveillance in survival disparities.