Diagnosis and Management of Rectal Neuroendocrine Tumors

Abstract

The incidence of rectal neuroendocrine tumors (NETs) has increased by almost ten-fold over the past 30 years. There has been a heightened awareness of the malignant potential of rectal NETs. Fortunately, many rectal NETs are discovered at earlier stages due to colon cancer screening programs. Endoscopic ultrasound is useful in assessing both residual tumor burden after retrospective diagnosis and tumor characteristics to help guide subsequent management. Current guidelines suggest endoscopic resection of rectal NETs ≤10 mm as a safe therapeutic option given their low risk of metastasis. Although a number of endoscopic interventions exist, the best technique for resection has not been identified. Endoscopic submucosal dissection (ESD) has high complete and en-bloc resection rates, but also an increased risk of complications including perforation. In addition, ESD is only performed at tertiary centers by experienced advanced endoscopists. Endoscopic mucosal resection has been shown to have variable complete resection rates, but modifications to the technique such as the addition of band ligation have improved outcomes. Prospective studies are needed to further compare the available endoscopic interventions, and to elucidate the most appropriate course of management of rectal NETs.

Endoscopic Resection of a Rectal Neuroendocrine Tumor: Hybrid Endoscopic Submucosal Dissection

“…Endoscopic resection plays a central role in the resection of small well-differentiated R-NET (< 10 mm) and selected cases measuring 10–20 mm, given the low risk of metastasis [2-4]. There is no consensus regarding the best endoscopic resection technique [1, 2, 4, 5], including conventional polypectomy, endoscopic mucosal resection (EMR) or ESD. Conventional polypectomy should be avoided as complete resection is often not achieved [1, 4] and EMR shows a suboptimal complete resection rate (30–70%) due to frequent submucosal involvement affecting mostly the vertical margin [1, 3, 5].…”

“…There is no consensus regarding the best endoscopic resection technique [1, 2, 4, 5], including conventional polypectomy, endoscopic mucosal resection (EMR) or ESD. Conventional polypectomy should be avoided as complete resection is often not achieved [1, 4] and EMR shows a suboptimal complete resection rate (30–70%) due to frequent submucosal involvement affecting mostly the vertical margin [1, 3, 5]. Incomplete resection requires endoscopic retreatment with additional difficulty due to submucosal fibrosis, surgery and/or long-term follow-up.…”

“…Despite the increasing incidence due to the widespread use of screening colonoscopy, R-NET are relatively rare and often well differentiated [1-5]. Endoscopic resection plays a central role in the resection of small well-differentiated R-NET (< 10 mm) and selected cases measuring 10–20 mm, given the low risk of metastasis [2-4].…”

“…Incomplete resection requires endoscopic retreatment with additional difficulty due to submucosal fibrosis, surgery and/or long-term follow-up. Alternatively, ESD has a higher complete resection rate (80–100%) with the disadvantage of being a complex and time-consuming procedure and an increased risk of complications [1-4]. …”

“…Recently, modified EMR (cap- or band ligation-assisted), hybrid EMR/ESD (H-EMR/ESD) techniques, and full-thickness resection [1, 3-5] have been proposed to improve in-depth resection of conventional EMR and decrease ESD drawbacks [3-5]. These techniques have a comparable complete resection rate (70–100%) and similar safety profile as ESD, but with a shorter procedure time [1-4].…”