In a cohort study, incidences of colorectal cancer were similar between individuals who had intermediate-risk adenomas removed and the general population. However, the number of cancers in the adenoma cohort is inflated by surveillance colonoscopy activities, resulting in lead-time bias and possible over-diagnosis bias. We showed in a previous study with a similar design that because of these and other biases colorectal cancer incidence is an unreliable endpoint, and instead suggested to report estimates of colorectal cancer mortality, which are less prone to bias in this setting.