Postpolypectomy risk stratification guidelines from the U.S. and U.K. compared

Guidelines used in the United Kingdom to stratify postpolypectomy patients may more accurately predict risk of advanced colorectal neoplasia than current U.S. guidelines, a study found.

Researchers conducted a pooled analysis of four prospective studies involving 3,226 postpolypectomy patients treated at academic and private clinics in the U.S. between 1984 and 1998. All of the studied patients received an initial polypectomy and then a follow-up colonoscopy six to 18 months later. The analysis measured rates of advanced neoplasia (defined as an adenoma ≥ 1 cm, high-grade dysplasia, > 25% villous architecture or invasive cancer) found at follow-up. Results appeared in the Dec. 18 Annals of Internal Medicine.

When patients were stratified by the U.S. criteria, 11.2% of higher-risk patients and 3.8% of lower-risk patients had advanced neoplasia at follow-up. Use of U.K. criteria found 4.4% of low-risk patients, 9.9% of intermediate-risk patients and 18.7% of high-patients to have advanced neoplasia. All of the U.S. guidelines' lower-risk patients were considered low risk by the U.K. guidelines, too. The U.S. guidelines' higher-risk patients were distributed across all three of the U.K. categories.

Under the U.K. guidelines, high-risk patients would receive a clearing colonoscopy at one year instead of waiting three years. Researchers calculated that following this criterion and recommendation would have detected advanced adenomas 2 years earlier in 19% with lesions at 1 year, while requiring 0.03 more colonoscopies per 5 years for all followed patients.

Another major difference between the guidelines is that the U.K. set does not consider histologic features, the authors noted. This resulted in more patients being classified as low risk under the U.K. system. Those patients were found more likely to have advanced neoplasia than others in the U.K. low-risk group, suggesting that histologic characteristics might provide a modest additional amount of discrimination, the authors said. They called for further study of this area.

Finally, they noted that “quality of the initial colonoscopy may be the principal determinant of 1-year advanced colorectal neoplasia,” indicating the importance of colonoscopy improvement efforts.