Systematic review with meta-analysis: the incidence of advanced neoplasia after polypectomy in patients with and without low-risk adenomas

Background Patients with one to two tubular adenomas <1cm in size without high-grade dysplasia (low-risk group) are considered at low risk for colorectal cancer. However, it is uncertain whether they have the same risk of subsequent advanced neoplasia as those with no neoplasia at baseline colonoscopy. Aim To compare incidence of metachronous advanced neoplasia between patients in the low-risk adenoma group and those without neoplasia at index colonoscopy. Methods Relevant publications were identified by MEDLINE/EMBASE and other databases for the period 1992-2013. Studies comparing the incidence of post-polypectomy advanced neoplasia (adenomas >= 10mm/high-grade dysplasia/villous or cancer) between the low-risk group and patients without colorectal neoplasia at the first colonoscopy were included. Detection rates for advanced neoplasia at endoscopic surveillance were extracted. Study quality was ascertained according to Newcastle-Ottawa Scale. Forest plot was produced based on random-effect models. Inter-study heterogeneity was assessed using the I-2 statistic. Results Seven studies provided data on 11387 patients. Mean surveillance periods ranged between 2 and 5years. Altogether, 267 patients with post-polypectomy advanced neoplasia were detected in the two groups. The incidence of advanced neoplasia was 1.6% (119/7308) in those without neoplasia and 3.6% (148/4079) in those with low-risk adenoma, respectively, corresponding to a relative risk of 1.8 (95% CI: 1.3-2.6). Inter-study heterogeneity was only moderate (I-2: 37%). No publication bias was present. Conclusions Patients with low-risk adenomas at baseline had a higher risk of metachronous advanced neoplasia than the group with no adenomas at baseline, though the absolute risk was low in both groups.