Gut Check on Gastroenterology Archive

Last week I heard one of our really talented GI fellows talking with a patient before her open access colonoscopy, and she told the patient that this test prevents colon cancer. I was somewhat surprised at the definitive implication of that statement and later asked her how much protection from colon cancer does colonoscopy screening provide? What really shocked me was her response that the protective value of colonoscopy was nearly 100%!

Unfortunately, I think her estimate is both widespread and incorrect. Most recent estimates are that colonoscopy decreases the incidence of colorectal cancer by approximately 70% to 80%, a remarkable figure that substantiates that colonoscopy is by far the best cancer-prevention strategy of any currently practiced screening test, including mammography, PAP smears, and PSA screening. But it it does not provide the 100% protection assumed by gastroenterologists, other healthcare providers, and patients.

Why aren’t we able to achieve 100% protection with this test? There are many likely reasons including imperfect colonoscopy (we miss lesions) and biological behavior of colon neoplasms (microsatellite unstable lesions and the like) that allow for “interval” cancers to develop.

So why the discrepancy between reality (colonoscopy is a great cancer prevention test but not perfect) and perception (colonoscopy guarantees cancer prevention)? I think that it is not because we are being disingenuous but rather that we are being naïve and have not followed the literature very closely and that our patients are sometimes blinded by their hope and optimism. We really need to make sure that they understand the need for colon cancer prevention screening with colonoscopy but also that the test has limitations.

What do you tell your patients when you are referring them for colonoscopy or before you do perform the screening? How protective do you think the test is? Do you think it eventually will get better with improvements in technology? How can we reduce misperceptions–both our own and our patients’–about this test?