Long-term outcomes of endoscopic resection of 1-1.5 cm sized grade 1 rectal neuroendocrine tumor: A retrospective study.

Background: Rectal neuroendocrine tumors (NETs) smaller than 10 mm and well-differentiated tumors are generally considered to have a low risk of lymph node and distant metastasis, making them suitable for endoscopic resection. In contrast, tumors ≥ 20 mm in size typically require surgical resection. However, the optimal management of intermediate-sized (10-15 mm) rectal NETs remains controversial.

Aim: To compare the clinical outcomes of endoscopic resection of rectal NETs < 1 cm and those 1-1.5 cm in size.

Methods: A retrospective study was conducted on 1056 patients with rectal NETs treated at the Samsung Medical Center between January 2005 and June 2021. After propensity score matching (1:10) for age, sex, and type of endoscopic resection, 225 patients with tumors < 1 cm in size and 27 patients with tumors 1-1.5 cm in size were analyzed.

Results: Surgical resection was more frequent in the 1-1.5 cm group (37.2%) than in the < 1 cm group (10.7%) (P < 0.01). Endoscopic submucosal dissection was also more commonly performed in the 1-1.5 cm group (48.1% vs 18.5%, P < 0.01). Negative resection margins were achieved in 97.2% of the patients, with no significant difference between the groups (P = 0.22). No lymphovascular invasion was observed. During a median follow-up of 54 months, no recurrence occurred in the 1-1.5 cm group, while one case of metachronous recurrence was noted in the < 1 cm group (P = 1.00). There was no significant difference in recurrence-free survival (P = 0.48).

Conclusion: Endoscopic resection of 1-1.5 cm grade 1 rectal NETs yielded comparable outcomes to those < 1 cm in size, suggesting its feasibility as a treatment.