Abstract
BACKGROUND/AIMS: Western surveillance strategies cannot be directly adapted to the Korean population. The aim of this study was to estimate the risk of metachronous neoplasia and the optimal surveillance interval in the Korean population. METHODS: Clinical and pathological data from index colonoscopy performed between June 2006 and July 2008 and who had surveillance colonoscopies up to May 2015 were compared between low- and high-risk adenoma (LRA and HRA) groups. The 3- and 5-year cumulative risk of metachronous colorectal neoplasia in both groups were compared. RESULTS: Among 895 eligible patients, surveillance colonoscopy was performed in 399 (44.6%). Most (83.3%) patients with LRA had a surveillance colonoscopy within 5 years and 70.2% of patients with HRA had a surveillance colonoscopy within 3 years. The cumulative risk of metachronous advanced adenoma was 3.2% within 5 years in the LRA group and only 1.7% within 3 years in the HRA group. The risk of metachronous neoplasia was similar between the surveillance interval of <5 and ≥5 years in the LRA group; however, it was slightly higher at surveillance interval of ≥3 than <3 years in the HRA group (9.4% vs. 2.4%). In multivariate analysis, age and the ≥3-year surveillance interval were significant independent risk factors for metachronous advanced adenoma (P=0.024 and P=0.030, respectively). CONCLUSIONS: Patients had a surveillance colonoscopy before the recommended guidelines despite a low risk of metachronous neoplasia. However, the risk of metachronous advanced adenoma was increased in elderly patients and those with a ≥3-year surveillance interval.