Endoscopic resection using an over-the-scope clip for duodenal neuroendocrine tumors

Background and study aims  Endoscopic resection of duodenal neuroendocrine tumors (DNETs) remains controversial, and its indications are still unclear. This study aimed to evaluate short-term outcomes of a newly developed endoscopic muscularis resection (EMR) method that utilizes an over-the-scope clip (OTSC), termed EMRO, for treating DNETs. Patients and methods  In total, 13 consecutive patients with 14 small (≤ 10 mm) DNETs who underwent EMRO from September 2017 to March 2020 were retrospectively enrolled. EMRO was performed by a single experienced endoscopist. Patients' characteristics and treatment outcomes were assessed. Results  The En bloc and R0 resection rates were 100 % (14/14) and 92.9 % (13/14), respectively. The median pathological resected specimen size was 10 mm, with a median pathological resected tumor size of 6 mm. During the EMRO procedure, there was no occurrence of misplacement of the OTSC to the target lesion. With respect to the pathological resection depth, nine cases (64.3 %) and five cases (35.7 %) were categorized as deep submucosal resection and muscularis resection, respectively, whereas no case was categorized as full-thickness resection. There were no intraoperative or delayed perforations. However, delayed bleeding occurred in two cases. At a median follow-up of 12 months (range 7-36) after EMRO, there was no incidence of local recurrence. At the first follow-up endoscopy performed at 6 months after EMRO, the OTSC was retained in place in two of 14 DNETs (14.3 %). Conclusions  EMRO can be performed safely, by an experienced endoscopist, for small (≤ 10 mm) DNETs.