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.