Risk of colorectal cancer among Caucasian and African American veterans with ulcerative colitis*

Abstract

African Americans are at an increased risk of developing sporadic colorectal cancer (CRC) compared to Caucasians. Ulcerative colitis (UC) is a risk factor for developing CRC; however, risk differences for CRC between African Americans and Caucasians with UC are unknown. We performed a cohort study of patients with a diagnosis of UC during fiscal years 1998 to 2009 using the national Veterans Affairs administrative datasets. Cumulative CRC incidence rates and incidence rate ratios were calculated and Cox proportional hazards models were used to examine the association between race and the CRC risk. The cohort comprised of 20,949 patients with UC. A total of 168 incident cases of CRC were identified during 112,243 patient-years (PY) of follow-up; overall CRC incidence rate was 163/100,000 PY (95% confidence interval [CI] 139-187/100,000 PY). The CRC incidence rates were 158/100,000 PY (95% CI 134-181/100,000 PY) and 180/100,000 PY (95% CI 155-205/100,000 PY) in Caucasians and African Americans, respectively, with an incidence rate ratio of 1.17 (95% CI 0.69-1.97). The 3, 5, and 10-year cumulative incidence rates for CRC were 0.36%, 0.76%, 1.79% for African Americans and 0.41%, 0.76%, 1.43% for Caucasians. African Americans were not at an increased risk for CRC (adjusted hazard ratio: 1.10, 95% CI 0.65-1.87) compared to Caucasians. In a national cohort of UC patients the risk of developing CRC in African Americans was no higher than in Caucasians. The reasons for lack of racial differences compared to sporadic CRC are not clear; access to care, genetic factors, and molecular pathways require further study.