To the Editor: As authors of one of the studies quoted by Drs Neugut and Lebwohl1 (reference 8 in their Commentary) and another more recent study on colorectal cancer mortality after colonoscopy,2 we would like to emphasize that the results of recent observational studies on colonoscopy outcomes should not be interpreted to imply that colonoscopy has no definite effect on proximal colorectal cancers. Indeed, these studies in all likelihood included some individuals at higher risk of developing colorectal cancer, such as those with a colorectal cancer family history. Especially in Canada, where 2 of the studies were conducted, there has been a greater impetus to screen higher-risk individuals than average-risk persons with colonoscopy. Hence, it is possible that colonoscopy may have actually reduced the risk of proximal colorectal cancers in such individuals from the baseline higher risk to that in the general population.
Singh H, Demers AA, Bernstein CN. Screening Colonoscopy vs Flexible Sigmoidoscopy. JAMA. 2010;304(18):2016-2018. doi:10.1001/jama.2010.1585