Current guidelines for colonoscopic follow-up after polypectomy are based on a risk stratification scheme that is only modestly accurate in predicting development of advanced adenomas, researchers have found.

In 2006, the American Cancer Society and the US Multi-Society Task Force on Colorectal Cancer teamed up to create a consensus update for postpolypectomy surveillance guidelines. For patients classified as high-risk - those with three or more synchronous adenomas or with any advanced adenoma - repeat colonoscopy in three years was advised. For patients with fewer, nonadvanced adenomas, a five- to ten-year surveillance interval was recommended.

Many gastroenterologists, however, have questioned the predictive value of these guidelines, according to the report in the Annals of Internal Medicine for March 18. As a result, adherence with the guidelines has been low.

To determine whether clinicians' concerns are valid, Dr. Adeyinka O. Laiyemo, from the NCI in Bethesda, Maryland, and associates analyzed prospective data from 1905 patients enrolled in the Polyp Prevention Trial. The subjects had an adenoma removed at baseline and then underwent repeat colonoscopy at one year and four years.

Advanced and nonadvanced adenoma recurrence within four years was documented in 6.6 per cent and 33.0 per cent of patients, respectively. For high-risk patients, the probability of advanced adenoma recurrence was nine per cent, whereas for low-risk patients, the probability was five per cent.

High-risk patients were 68 per cent more likely than low-risk patients to have recurrence of an advanced rather than a non-advanced adenoma. Similarly, high-risk status increased the odds of advanced adenoma recurrence compared with no adenoma recurrence by 76 per cent.

"Our study suggests that the adenoma-based risk stratification used in the current postpolypectomy surveillance guidelines have limited predictability for advanced adenoma recurrence," the authors conclude.

In an accompanying commentary, Dr. Thomas F. Imperiale, from Indiana University in Indianapolis, and editor Dr. Harold C. Sox note that to effectively counsel postpolypectomy patients, "We need to provide them with better data about the probability of malignant transformation at the recommended surveillance interval."

They add, "Until these quantitative issues are addressed, our decision making should start with published recurrence rates and then be tailored further by taking into account individual patient features, such as age, nonsteroidal anti-inflammatory drug use, life expectancy, comorbid conditions, and preferences."

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