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Physicians May Increase Screening Intervals for Patients at Low Risk for Colon Polyps

August 5, 2009

Dr. Robertson

Douglas Robertson, MD, MPH

A team of Dartmouth Medical School and VA Medical Center researchers have determined that surveillance intervals for patients at low risk for colon adenomas (polyps) could be increased, based on prior exams. The team, led by Douglas J. Robertson, MD, MPH, calculated the probability of high-risk findings on a third colonoscopy for patients with a past colon adenoma, using results from the first and second follow-up.

Physicians commonly perform surveillance colonoscopies on patients who have had a past adenoma. Guidelines have been established for clinicians to determine the appropriate intervals for surveillance. High-risk patients should have a follow-up screening at three years, while low-risk patients can wait five to ten years. However, the criteria for choosing between five- and ten-year follow-up is not clear.

To help establish an appropriate screening interval, researchers studied patients who had two surveillance colonoscopies after a baseline colonoscopy that showed adenoma. They used the results from the first and second colonoscopies to determine the probability of high-risk findings on a third colonoscopy. Researchers found that patients with advanced or multiple adenomas on both the first and second colonoscopy had a relatively high likelihood (18.2%) of high-risk findings at the third examination. Conversely, relatively few participants (5.0%) that had low-risk findings on their first two examinations had high-risk results on their third colonoscopy.

These findings, published in the July issue of Annals of Internal Medicine, suggest that a longer follow-up interval may be appropriate for lower risk patients, as determined by their adenoma history.