Assessing risk stratification in long-term outcomes of rectal neuroendocrine tumors following endoscopic resection: A multicenter retrospective study.

Abstract

42 Background: The detection of rectal neuroendocrine tumors (NETs) has increased with advances in diagnostic endoscopy. Endoscopic resection (ER) is a highly effective treatment option for rectal NETs confined to . We aimed to analyze the long-term outcomes of patients with rectal NETs after ER. Methods: In this multicenter retrospective study, we included patients who underwent ER of rectal NETs from 2009 to 2018 and were followed for ≥12 months at five university hospitals. We classified the patients into three risk groups according to the clinicopathological status of the rectal NETs: low, indeterminate, and high. The high-risk group was defined if the tumors have any of the followings: size ≥ 10 mm, lymphovascular invasion, muscularis propria or deeper invasion, positive resection margins, or mitotic count ≥2/10. Results: In total, 346 patients were included, with 144 (41.6%), 121 (35.0%), and 81 (23.4%) patients in the low-, indeterminate-, and high-risk grouprespectively. In the high-risk group, seven patients (7/81, 8.6%) received salvage treatment 28 (27–67) days after the initial ER. There was no extracolonic recurrence in any of the 7 patients. During the follow-up period of all included patients, 1.1% (4/346) had extracolonic recurrences at 56.5 (54–73) months after initial ER. Three of these patients (75%) were at a high risk without salvage treatment. The risk of extracolonic recurrence was significantly higher in the high-risk group than in the other groups (p=0.039). Conclusions: The prognosis of patients who underwent ER for rectal NETs was favorable. Physicians should be concerned about the possibility of metastasis during long-term follow-up of high-risk patients and consider salvage treatment. [Table: see text]