Pinsky PF, et al. - Considering that the contribution of surveillance colonoscopy to the prevention of colorectal cancer (CRC) is not clear as opposed to that of initial colonoscopy examination, researchers estimated the preventive impact of surveillance colonoscopy by applying the recently developed adenoma dwell time metric that was avoided to prevent 1 CRC case (DTA). Participants in the prostate, lung, colorectal and ovarian (PLCO) cancer screening trial were followed who had colonoscopies after positive findings from sigmoidoscopies (colonoscopy cohort, n=15,935) for CRC incidence for 10 years. Two thousand eight hundred eighty-two participants had advanced adenomas (AAs) in the PLCO colonoscopy cohort, 572 had 3 or more non-advanced adenomas (NAA3₊), 4,496 had 1–2 non-advanced adenomas (NAA_1-2), and 7,985 had no adenoma (NA). The authors estimated that surveillance colonoscopy during 10 years of follow up (in the PLCO colonoscopy cohort) prevented 30% of CRC cases utilizing the recently developed metric of DTA. Since the estimation methodology is indirect the true effect is uncertain.