[Analysis on risk factors of positive vertical resection margin after endoscopic treatment of rectal neuroendocrine tumors].

Objective: To analyze the risk factors of positive vertical resection margin of the postoperative specimens after endoscopic treatment of rectal neuroendocrine tumors (NET). Methods: A case-control study was performed. Clinical data of patients with rectal NET (G1) undergoing endoscopic treatment between January 2015 and June 2018 at the Department of Gastroenterology, Beijing Tsinghua Changgung Hospital were retrospectively collected. Inclusion criteria: cases underwent endoscopic mucosal resection (EMR) or endoscopic submucosal dissection (ESD), whose mucosal specimens were pathologically confirmed as NET, and NET was confined to the rectum by nuclide imaging examination before endoscopic treatment. Those with incomplete clinical data or follow-up data were excluded. Resected specimen was fixed and sliced every 2 mm, and when tumor cells were found to infiltrate the vertical cutting edge, the positive vertical margin was defined. Associations of gender, age, resection method, tumor diameter, lesion morphology (nodular lesions, biopsy or post-treatment scar-like changes), mitotic figure, Ki-67 index, etc. and positive vertical margin were analyzed. Univariate analysis was performed using binary logistic analysis and multivariate analysis was performed using logistic regression model. Results: A total of 133 patients with rectal NET were enrolled, including 93 males and 40 females, with an average age of (50.0±10.7) years. Sixty-four patients received EMR treatment and 3 patients (4.7%) had positive vertical margins. While 69 patients received ESD treatment and 13 (18.8%) had positive vertical margins. After endoscopic treatment, 16 cases (12.0%) were vertical positive margin, including 11 males and 5 females with an average age of (52.4±10.4) years. The lesion diameter was (9.0±4.7) mm. Univariate analysis showed that lesion diameter ≥10 mm (χ(2)=5.575, P=0.018) and scar-like changes (χ(2)=3.894, P=0.048) were significantly associated with positive vertical margin. Multivariate analysis showed that the lesion diameter ≥10 mm (OR=10.136, 95%CI: 2.114 to 48.591, P=0.004) was an independent risk factor for positive vertical margin of the specimen after endoscopic treatment of rectal NET. Conclusion: The diameter of rectal NET ≥10 mm indicates a high risk for positive vertical margin after endoscopic treatment.