The risk of advanced neoplasia after polypectomy of one to two non-advanced adenomas less than 5 mm in size vs. normal colonoscopy

Background: Current guidelines are inconsistent regarding the follow-up of patients with 1–2 diminutive (1–5 mm) non-advanced adenomas (DNAAs). Aims: To evaluate the risk of metachronous advanced neoplasia (AN), defined as cancer or advanced adenoma (AA), among patients with either normal colonoscopy or 1–2 DNAAs. Methods: A retrospective cohort study. Cohort I included 2,347 subjects with normal colonoscopy and 483 subjects with polypectomy of 1–2 DNAAs followed by colonoscopy. Cohort II included 11,881 subjects with normal colonoscopy and 1,342 subjects with 1–2 DNAAs followed through the cancer registry. Results: In cohort I, the rate of AN, cancer and AA among the polypectomy group vs. normal colonoscopy was 5.0% vs. 2.5%, Hazard Ratio (HR) 2.96 (95%CI [Confidence Interval]1.86–4.78) for AN; 0.6% vs. 0.3%, HR 3.32 (95%CI 0.85–13) for cancer; 4.3% vs. 2.2% HR 2.91 (95%CI 1.75–4.86) for AA. In cohort II, cancer occurred in 0.4% of the polypectomy group and 0.2% of the normal colonoscopy group, HR 2.27 (95% CI 0.56–9.19). Conclusion: Compared to subjects with normal colonoscopy, subjects with polypectomy of 1–2 DNAAs, are at increased risk for AA when followed by colonoscopy, while the risk for cancer is non-significantly increased. Our findings suggest that patients with 1–2 DNNAs should be followed more tightly than patients with normal colonoscopy.