Local Recurrence Rate of Rectal Carcinoid Tumors After Endoscopic Mucosal Resection With Transrectal Ultrasound

Abstract

Introduction: Rectal carcinoids are the most common neuroendocrine tumors of the GI tract. They constitute 1-2% of all rectal tumors. Incidence of rectal carcinoids is on the rise due to more frequent surveillance colonoscopies. The overall metastatic risk of small well-differentiated rectal carcinoids tumor is low but not negligible. However, local recurrence of the tumors, especially with respect to resection margin status has not been clearly established. Methods: We performed a retrospective cohort study (2007-2017) of a single tertiary center using pathology database for well differentiated neuroendocrine tumors of the rectum as well as electronic medical record search for all transrectal ultrasound procedures performed. All patients over age of 18 were included. Patient with malignant neuroendocrine tumors with distal metastases and patients who underwent surgical resection of the tumors were excluded. Results: We identified 74 patients. (34 males, 40 females; 44 African Americans, 20 Whites, 5 Asians, 5 Others; Age 54.4, 23-77). The average resected tumor size was 0.49 cm (0.1-1.2cm). All tumors were initially discovered on colonoscopy. Endoscopic technique used for resection: 51 Colonoscopy (hot/cold snare polypectomy), 28 transrectal ultrasound (RUS) (endoscopic mucosal resection). Endoscopic mucosal resection under ultrasound was more likely to achieve negative margin (Resection rate (28/28, 100%, P < 0.0001). 5 cases of incomplete resection with colonoscopic polypectomy (5/51, resection rate of 90.2%) were later resected with follow up RUS EMR without recurrence. There is no difference between resection margin and recurrence with EMR under RUS (P = 0.99). There is 1 case of synchronous NET with EMR during follow up at a different location in the rectum. Average endoscopic follow up time is 14.8 months (0-138). 48 Patients had endoscopic follow up, 25 patients had imaging follow up (MRI and CT). 19 Patients did not have any follow up. Conclusion: Local recurrence rate of small well differentiated rectal carcinoid tumors after endoscopic mucosal resection under rectal ultrasound is very low and independent of resection margin status. Resection of rectal carcinoids with conventional, colonoscopic polypectomy may be incomplete if the margins are positive, necessitating close endoscopic follow up.818 Figure 1. Comparison between colonoscopy (Polypectomy) and rectal ultrasound (EMR) with respect to resection margin status and recurrence/incomplete resection.