Incidence of colorectal adenomas: birth cohort analysis among 4.3 million participants of screening colonoscopy.

BACKGROUND Most colorectal cancers develop from adenomas. We aimed to estimate sex- and age-specific incidence rates of colorectal adenomas and to assess their potential implications for colorectal cancer screening strategies. METHODS Sex- and age-specific incidence rates of colorectal adenomas were derived by a birth cohort analysis using data from 4,322,085 screening colonoscopies conducted in Germany and recorded in a national database in 2003-2012. In addition, cumulative risks of colorectal cancer among colonoscopically neoplasm-free men and women were estimated by combining adenoma incidence rates with previously derived adenoma-colorectal cancer transition rates. RESULTS Estimated annual incidence in percentage (95% confidence interval) in age groups 55-59, 60-64, 65-69, 70-74, and 75-79 was 2.4 (2.2-2.6), 2.3 (2.1-2.6), 2.4 (2.1-2.6), 2.2 (1.8-2.5), and 1.8 (1.2-2.3) among men, and 1.4 (1.3-1.5), 1.5 (1.4-1.7), 1.6 (1.4-1.8), 1.6 (1.3-1.8), and 1.2 (0.8-1.6) among women. Estimated 10- and 15-year risks of clinically manifest colorectal cancer were 0.1% and 0.5% or lower, respectively, in all groups assessed. CONCLUSIONS Annual incidence rates of colorectal adenomas are below 2.5% and 2% among men and women, respectively, and show little variation by age. IMPACT Risk of clinically manifest colorectal cancer is expected to be very small within 10 years and beyond after negative colonoscopy for men and women at all ages. The use of rescreening after a negative screening colonoscopy above 60 years of age may be very limited.