Screening Colonoscopy vs Flexible Sigmoidoscopy—Reply

In Reply: We agree with the letter writers that colonoscopy should remain in place as a colorectal screening tool. Our Commentary was intended to highlight the accumulating evidence regarding its effectiveness in reducing cancer incidence and mortality in the proximal colon and the need for further research on this issue. However, if more substantial evidence confirms the 3 studies we cited, questions should be raised regarding the primacy of colonoscopy.

As both letters affirm, the reasons for the lack of effect of colonoscopy in the proximal colon may reflect correctable problems, such as the specialty and skill of the colonoscopist or other variations in performance. Nonetheless, these data reflect how colonoscopy is currently performed on a population scale, at least in Canada and Germany. Whether colonoscopy by a cadre of extremely expert colonoscopists would yield improved right-sided mortality is only speculative. But what matters is what happens in the real world (the distinction between effectiveness and idealized efficacy).