Selective colonization with Helicobacter bilis or Escherichia coli induces differential host immune responses following an inflammatory trigger.

Abstract

BACKGROUND/AIMS: Ulcerative colitis (UC) is a risk factor for developing colorectal cancer (CRC). African Americans are at an increased risk of developing sporadic CRC compared to Caucasians. It is unknown if risk disparity for CRC exists for African-Americans and Caucasians with UC. METHODS: We performed a cohort study of patients identified with UC during fiscal years 1998 to 2009 in the national Veterans Affairs (VA) administrative datasets, specifically the Patient Treatment Files (PTF) and the Outpatient Care (OPC) files. We required two International Classification of Diseases, 9th Revision (ICD-9) diagnosis codes for UC (556.x) with at least one code from an outpatient encounter for inclusion. The first VA encounter with a UC code was considered to be the index date for follow-up. Newly diagnosed CRC after the first year of follow-up were identified based on ICD-9 codes (153.x or 154.x) with at least one inpatient or two outpatient diagnosis codes. Last date of follow-up was the earliest of date of CRC, death, last VA encounter or September 30th, 2009. Race information was obtained from multiple sources and the assignment was performed according to previously published algorithms. Cumulative CRC incidence rates and rate ratios were calculated for the entire cohort and for blacks and whites separately. Cox proportional hazards model was used to examine the association between race and the risk of CRC while adjusting for age and gender. RESULTS: The cohort comprised of 20,949 patients with UC; 95% were males and the racial distribution was 7% African American, 71% Caucasian, 3% Hispanic, 2% other and 17% unknown. Mean age at index VA encounter with UC was 61.6 years (SD 14.6). A total of 168 incident cases of CRC were identified (97% male, 10% African American, and 79 % Caucasian) during 112,243 patient-years (PY) of follow up; crude incidence CRC rate = 163/100,000 PY. The cumulative CRC incidence rates were 158/100,000 PY and 180/100,000 PY for Caucasians and African Americans, respectively, with an incidence rate ratio (IRR) 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; the incidence rate ratios were 0.88 (0.35-2.20), 0.97 (0.49-1.93), and 1.12 (0.66-1.92), respectively (with 95% CI). In a Cox proportional hazard model, African Americans were not at an increased risk for CRC (adjusted HR: 1.13, 95% CI 0.67-1.92) compared to Caucasians. CONCLUSIONS: In the largest US cohort of patients with UC, African Americans were not more likely to develop CRC compared to Caucasians. The reasons for lack of racial disparity when compared to sporadic CRC are not clear. Access to CRC screening, genetic factors, and differences in pathways to CRC in sporadic vs. UC associated CRC need to be examined.