Racial disparities in colon cancer survival: A matched cohort study

Background: Differences in colon cancer survival by race are a recognized problem among Medicare beneficiaries. Objective: To determine to what extent the racial disparity in survival is due to disparity in presentation characteristics at diagnosis or disparity in subsequent treatment. Design: Black patients with colon cancer were matched with 3 groups of white patients: a "demographic characteristics" match controlling for age, sex, diagnosis year, and Survey, Epidemiology, and End Results (SEER) site; a "presentation" match controlling for demographic characteristics plus comorbid conditions and tumor characteristics, including stage and grade; and a "treatment" match, including presentation variables plus details of surgery, radiation, and chemotherapy. Setting: 16 U.S. SEER sites. Patients: 7677 black patients aged 65 years or older diagnosed between 1991 and 2005 in the SEER-Medicare database and 3 sets of 7677 matched white patients, followed until 31 December 2009. Measurements: 5-year survival. Results: The absolute difference in 5-year survival between black and white patients was 9.9% (95% CI, 8.3% to 11.4%; P < 0.001) in the demographic characteristics match. This disparity remained unchanged between 1991 and 2005. After matching for presentation characteristics, the difference decreased to 4.9% (CI, 3.6% to 6.1%; P < 0.001). After additional matching for treatment, this difference decreased to 4.3% (CI, 2.9% to 5.5%; P < 0.001). The disparity in survival attributed to treatment differences made up only an absolute 0.6% of the overall 9.9% survival disparity. Limitation: An observational study limited to elderly Medicare fee-for-service beneficiaries living in selected geographic areas. Conclusion: Racial disparities in colon cancer survival did not decrease among patients diagnosed between 1991 and 2005. This persistent disparity seemed to be more related to presentation characteristics at diagnosis than to subsequent treatment differences.