Surveillance after positive colonoscopy based on adenoma characteristics.

Background: Patients with adenomatous polyps are at increased risk for developing colorectal cancer based on the characteristics and number of polyps, but less is known about the individual and combined contribution of these factors. This study aimed to better characterize the risk of advanced adenoma and cancer in patients with positive baseline colonoscopy.

Methods: Patients who had polyps at baseline colonoscopy were included in this retrospective cohort study (N=1165) and were categorized into 6 groups: (1) 1-2 non-advanced adenomas (NAA's), (2) ≥3 NAA's, (3) advanced tubular adenoma, (4) small tubulovillous adenoma (TVA), (5) large TVA and (6) multiple advanced adenomas (MAA's). Findings at surveillance colonoscopy were documented in each group.

Results: The combined incidence of advanced adenoma,  ≥3 NAA's, and colorectal cancer at surveillance colonoscopy was significantly higher in the baseline large TVA (29.2%) than small TVA groups (13.5%, P<0.001), as well as in the MAA's group (44.1%) compared with large TVA group (P=0.02). The incidence of colorectal cancer, however, was not significantly different between the groups.

Conclusions: The size of the polyp and the number of advanced lesions are more important than its histology for predicting the risk of high-risk metachronous lesions at follow-up.