One-year risk for advanced colorectal neoplasia: U.S. Versus U.K. risk-stratification guidelines

Background: Guidelines from the United Kingdom and the United States on risk stratification after polypectomy differ, as do recommended surveillance intervals. Objective: To compare risk for advanced colorectal neoplasia at 1-year colonoscopy among patients cross-classified by U.S. and U.K. surveillance guidelines. Design: Pooled analysis of 4 prospective studies between 1984 and 1998. Setting: Academic and private clinics in the United States. Patients: 3226 postpolypectomy patients with 6- to 18-month follow-up colonoscopy. Measurements: Rates of advanced neoplasia (an adenoma ≥1 cm, high-grade dysplasia, >25% villous architecture, or invasive cancer) at 1 year, compared across U.S. and U.K. risk categories. Results: Advanced neoplasia was detected 1 year after polypectomy in 3.8% (95% CI, 2.7% to 4.9%) of lower-risk patients and 11.2% (CI, 9.8% to 12.6%) of higher-risk patients by U.S. criteria. According to U.K. criteria, 4.4% (CI, 3.3% to 5.4%) of low-risk patients, 9.9% (CI, 8.3% to 11.5%) of intermediate-risk patients, and 18.7% (CI, 14.8% to 22.5%) of high-risk patients presented with advanced neoplasia; U.K. high-risk patients comprised 12.1% of all patients. All U.S. lower-risk patients were low-risk by U.K. criteria; however, more patients were classified as low-risk, because the U.K. guidelines do not consider histologic features. Higher-risk U.S. patients were distributed across the 3 U.K. categories. Among all patients with advanced neoplasia, 26.3% were reclassified by the U.K. criteria to a higher-risk category and 7.0% to a lower-risk category, with a net 19.0% benefiting from detection 2 years earlier. Overall, substitution of U.K. for U.S. guidelines resulted in an estimated 0.03 additional colonoscopy every 5 years per patient. Limitations: Patients were enrolled 15 to 20 years ago, and quality measures for colonoscopy were unavailable. Patients lacking follow-up colonoscopy or with surveillance colonoscopy after 6 to 18 months and those with cancer or insufficient baseline adenoma characteristics were excluded (2076 of 5302). Conclusion: Application of the U.K. guidelines in the United States could identify a subset of high-risk patients who may warrant a 1-year clearing colonoscopy without substantially increasing rates of colonoscopy.