Race and Risk of Large Bowel Polyps in Younger and Older Patients

African Americans (AA) have a higher incidence of colorectal cancer (CRC) compared to European Americans (EA). However, AA are consistently diagnosed with CRC at a younger age suggesting a possible biologic difference in neoplasms by race. Few studies have investigated racial differences in risk of adenomas, precursors to most colorectal cancer and, to our knowledge, none have investigated whether this risk differs by adenoma type or age. To address this gap, we analyzed data pooled from three placebo-controlled adenoma chemoprevention trials to explore racial differences in the risk of large bowel polyps among younger and older subjects. Eligible subjects had at least one documented adenoma and were followed until their next scheduled colonoscopy. Using generalized linear regression, we estimated risk ratios and 95% confidence intervals (CI) as measures of the association between race and risk for one or more adenomas, advanced lesions, or hyperplastic polyps (HP) after randomization adjusting for age, sex, follow-up time, and treatment assignment. We defined advanced lesions as adenomas with at least 25% villous component, high-grade dysplasia, or an estimated size of 1 ≥ centimeter. We also assessed the potential interaction between race and age on the risk of large bowel polyps. Of the 2683 subjects enrolled, 2605 completed one follow-up exam after randomization (193 AA, 2412 EA). Overall, our results suggested a racial difference in risk for adenomas among younger (<50 years) but not among older (≥50 years) subjects (p-for interaction between age and race for any adenoma (p = 0.13) and for advanced adenoma (p = 0.04)). Younger AA, when compared to EA had a significantly higher risk of any adenoma (RR 1.73, 95% CI 1.00–3.00) and advanced lesions (RR 4.40, 95% CI 1.47–13.15) but no difference in risk of HP. Among older patients, using the same comparison, there was no racial difference in risk of adenomas (RR 1.06, 95% CI 0.91–1.25) or advanced lesions (RR 1.06, 95% CI 0.71–1.57)) but there was a significantly lower risk of HP (RR 0.64 (95% CI 0.47–0.88). Our findings suggest that older AA have a lower risk of HP; and AA under the age of 50 years of age are at increased risk of adenomas, especially advanced lesions.