Natural History of Colorectal Adenomas: Birth Cohort Analysis Among 3.6 Million Participants of Screening Colonoscopy

Background: Most colorectal cancers (CRC) develop from adenomas. Knowledge of the natural history of colorectal adenomas, which is not directly observable for ethical reasons, is crucial for designing cost-effective CRC screening strategies. Methods: We derived transition rates from carriage of nonadvanced adenoma to carriage of advanced adenoma to carriage of CRC by sex and age in birth cohort analyses among 3,593,420 participants in the German screening colonoscopy program in 2003-2010. Results: Transition rates from advanced adenoma to CRC carriage were similar in men and women, but monotonically and significantly increased with age. Estimated annual transition percentages [(95% confidence interval (CI)] in age groups 55-59, 60-64, 65-69, 70-74, and 75-79 years were 2.6 (2.4-2.9), 3.1 (2.8-3.3), 3.8 (3.5-4.1), 5.1 (4.8-5.5), and 5.2 (4.6-5.8) among men, and 2.5 (2.2-2.7), 2.7 (2.4-3.0), 3.8 (3.5-4.1), 5.0 (4.5-5.4), and 5.6 (4.9-6.3) among women. Estimated annual transitions from carriage of nonadvanced to carriage of advanced adenoma were in a narrow range from 3.6% to 4.7% for all age and sex groups. Conclusions: Despite low annual transition rates, cumulative transition rates from advanced adenoma to CRC carriage are expected to exceed by 60%, 50%, and 40% for age intervals 55-80, 65-80, and 70-80 years, respectively, in both sexes. Cumulative transition rates from nonadvanced adenoma to CRC carriage are expected to be close to 30% for age interval 55-80 years, but less than 2% for age interval 75-80 years. Impact: Our results enhance the empirical basis for modeling CRC screening strategies. (C) 2013 AACR.