Assessing individual risk for high-risk colorectal adenoma at first-time screening colonoscopy

Assessing risk of colorectal adenoma at first-time colonoscopy that are of higher likelihood of developing advanced neoplasia during surveillance could help tailor first-line colorectal cancer screening. We developed prediction models for high-risk colorectal adenoma (at least one adenoma ≥1 cm, or with advanced histology, or ≥3 adenomas) among 4,881 asymptomatic white men and 17,970 women who underwent colonoscopy as their first-time screening for colorectal cancer in two prospective US studies using logistic regressions. C-statistics and Hosmer-Lemeshow tests were used to evaluate discrimination and calibration. Ten-fold cross-validation was used for internal validation. A total of 330 (6.7%) men and 678 (3.8%) women were diagnosed with high-risk adenoma at first-time screening colonoscopy. The model for men included age, family history of colorectal cancer, BMI, smoking, sitting watching TV/VCR, regular aspirin/NSAID use, physical activity, and a joint term of multivitamin and alcohol. For women, the model included age, family history of colorectal cancer, BMI, smoking, alcohol, beef/pork/lamb as main dish, regular aspirin/NSAID, calcium, and oral contraceptive use. The C-statistic of the model for men was 0.67 and 0.60 for women (0.64 and 0.57 in cross-validation). Both models calibrated well. The predicted risk of high-risk adenoma for men in the top decile was 15.4% vs. 1.8% for men in the bottom decile (Odds Ratio [OR] = 9.41), and 6.6% vs. 2.1% for women (OR = 3.48). In summary, we developed and internally validated an absolute risk assessment tool for high-risk colorectal adenoma among the US population that may provide guidance for first-time colorectal cancer screening.