Factors That Contribute to Differences in Survival of Black vs White Patients With Colorectal Cancer

Published:November 13, 2017DOI:

      Background & Aims

      Previous studies reported that black vs white disparities in survival among elderly patients with colorectal cancer (CRC) were because of differences in tumor characteristics (tumor stage, grade, nodal status, and comorbidity) rather than differences in treatment. We sought to determine the contribution of differences in insurance, comorbidities, tumor characteristics, and treatment receipt to disparities in black vs white patients with CRC 18–64 years old.


      We used data from the National Cancer Database, a hospital-based cancer registry database sponsored by the American College of Surgeons and the American Cancer Society, on non-Hispanic black (black) and non-Hispanic white (white) patients, 18–64 years old, diagnosed from 2004 through 2012 with single or first primary invasive stage I–IV CRC. Each black patient was matched, based on demographic, insurance, comorbidity, tumor, and treatment features, with 5 white patients, from partially overlapping subgroups, using propensity score and greedy matching algorithms. We used the Kaplan-Meier method to estimate 5-year survival and Cox proportional hazards models to generate hazard ratios.


      The absolute 5-year survival difference between black and white unmatched patients with CRC was 9.2% (57.3% for black patients vs 66.5% for white patients; P < .0001). The absolute difference in survival did not change after patient groups were matched for demographics, but decreased to 4.9% (47% relative decrease [4.3% of 9.2%]) when they were matched for insurance and to 2.3% when they were matched for tumor characteristics (26% relative decrease [2.4% of 9.2%]). Further matching by treatment did not reduce the difference in 5-year survival between black and white patients. In proportional hazards model, insurance and tumor characteristics matching accounted for the 54% and 27% excess risk of death in black patients, respectively.


      In an analysis of data from the National Cancer Database, we found that insurance coverage differences accounted for approximately one half of the disparity in survival rate of black vs white patients with CRC, 18–64 years old; tumor characteristics accounted for a quarter of the disparity. Affordable health insurance coverage for all populations could substantially reduce differences in survival times of black vs white patients with CRC.


      Abbreviations used in this paper:

      CI (confidence interval), CRC (colorectal cancer), HR (hazard ratio), NCDB (National Cancer Data Base), NH (non-Hispanic)
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      1. Parsons LS. Reducing bias in a propensity score matched-pair sample using greedy matching techniques. Proceedings of the Twenty-sixth Annual SAS Users group international conference. SAS Institute, Cary, NC. 2001;26:214–226.