Long-term outcomes and surveillance timing of patients with large non-pedunculated colorectal polyps with histologically incomplete resection in endoscopic resection

Histologically incomplete resection of large colorectal polyps is frequently encountered; however, the long-term outcomes or surveillance timing is not well known. We evaluated the incidence rate and time of recurrence of these cases during a long-term follow-up. We performed a retrospective analysis of patients who underwent endoscopic resection for large (≥10 mm in size) non-pedunculated colorectal polyps at a tertiary academic hospital. Patients who had positive or indeterminate lateral margin in the histology and underwent completed surveillance colonoscopy first at 3–12 months and finally at ≥2 years after initial resection were included. Of 169 polyps (148 patients), 37 (21.9%) and 132 (78.1%) polyps had positive and indeterminate lateral margins, respectively. The median time intervals of the first and last surveillance from the initial resection were 6 (3–12) and 48 (24–114) months, respectively. The recurrence rate was 9.5% (16/169) during follow-up, and the mean time to recurrence was 31.9 months. Thirteen (81.3%) polyps recurred after ≥12 months. Most (14/16, 87.5%) recurrent polyps were benign, and 2 cases had advanced cancer. The only factor that was significantly associated with recurrence in the univariate and multivariate analyses was ≥3 piecemeal resections (odds ratio in the multivariate analysis, 16.92; 95% CI, 1.19–241.81; p = 0.037). During the long-term follow-up, the only factor that was significantly associated with recurrence was ≥3 piecemeal resections, and most recurrences occurred after ≥12 months. Thus, a histologically incomplete resection with ≤2 piecemeal resections and no findings of suspected submucosal cancer may be considered as complete resection, and these patients may undergo first surveillance colonoscopy after 1–2 years.