Clinical Utility of Rectal Endoscopic Ultrasound in Evaluation of Sub-centimeter Rectal Carcinoid Tumors

Abstract

Introduction: Rectal carcinoid tumors are often small and asymptomatic, usually diagnosed during screening colonoscopy, and up to 85% are localized at diagnosis. Lesions smaller than 1 cm are rarely metastatic, yet endoscopic ultrasound (EUS) is still commonly utilized to assess tumor depth and lymphadenopathy. EUS for sub-centimeter rectal carcinoid tumors may be exposing the patient to excess testing. Methods: All patients who underwent rectal EUS at our center from December 2013 to January 2017 were reviewed, and included if they had prior endoscopy demonstrating a nodule estimated to be 1 cm or less, with pathologic confirmation of carcinoid. There were no exclusion criteria beyond this. Pathology results, endoscopy results, adverse events, and repeat endoscopy results were reviewed. Results: 85 patients had rectal EUS, 23 for rectal carcinoid. Of these, 18 had initial nodules of 1 cm or smaller. Seventeen were found on screening colonoscopy, and one on colonoscopy for lower GI bleed. Rectal EUS was performed on average 47 days after initial procedure. No tumors were poorly differentiated. Average initial size estimation was 0.62 cm. EUS detected residual tumor on 3 of 18 (16.7%) cases, though biopsy or EMR of the area of initial lesion revealed residual tumor in 5 of 18 (27.8%). No lymphadenopathy was seen, and only one case had extension of tumor into submucosa, with pathology from EMR demonstrating negative margins. There were no adverse events due to the EUS procedure, though one patient had post-procedural bleeding requiring repeat endoscopy following EMR. Seven patients had follow up endoscopy within our system, with no recurrent disease. Conclusion: EUS is typically done for evaluation of rectal carcinoid tumors, though the data to support its use in small tumors is lacking. Although rectal EUS is regarded as a low-risk procedure, there are medical risks and financial implications to its performance. We have demonstrated that in our cohort, EUS prior to biopsy or EMR of the site of rectal carcinoid does not change management. Our study does have limitations in that it is a small, single center descriptive study. Additionally, due to the referral nature of our practice, follow up data is not available for over half of the patients, meaning we may not be capturing patients with recurrent disease. Despite this, our data suggest that EUS may be unnecessary for small rectal carcinoid tumors.