The meaning of R1 resection after endoscopic removal of gastric, duodenal and rectal neuroendocrine tumors

ABSTRACT

Introduction

Well-differentiated gastric, duodenal, and rectal neuroendocrine neoplasms (NETs) are rare diseases usually managed by endoscopic treatment. Although several endoscopic techniques are available, the number of patients with incomplete (R1) resection is significant.

Areas covered

This review focuses on the meaning of incomplete R1 findings after endoscopic resection in type I gastric NETs; nonfunctioning, non-ampullary duodenal NETs; and small rectal NETs. Data were identified by MEDLINE database search without publication date limitation.

Expert opinion

An incomplete R1 finding may have no significant impact on a patient’s clinical outcome, particularly in small G1 type I gastric NETs, which have an indolent course. A ‘stepwise approach,’ which uses more advanced endoscopic techniques, or minimally invasive surgery may be justified to achieve complete margin-free resection. This approach must balance the tumor features and the procedure-related risk of complications, particularly in the duodenum, where the role of deep endoscopic resections is limited due to the thin duodenal wall. Gastric and rectal NETs that are incompletely removed after initial resection are more easily amenable to deep endoscopic techniques. However, this might not be necessary for patients with comorbidities, elderly, or both due to the uncertainty of how R1 finding impacts a patient’s clinical outcome.

KEYWORDS:

• endoscopy
• neuroendocrine tumors
• stomach
• rectum
• duodenum
• tumor progression
• residual disease
• polypectomy

Article highlights

• The best endoscopic technique for achieving complete margin-free tumor resection in gastric, duodenal, and rectal well-differentiated NETs still needs to be established.

• Endoscopic submucosal dissection is effective at obtaining deep complete resection. However, caution should be used when planning this kind of resection, particularly in the duodenum, given the high risk of major complications.

• Snare polypectomy should be avoided due to the high probability of obtaining an incomplete R1 tumor resection.

• EMR and its modified variations are recommended, particularly in patients who stand a high risk of complications. This approach is also preferred at the duodenal site, where ESD is not recommended due to the risk of bleeding and perforation.

• In case of an R1 finding after endoscopic resection of gastric, duodenal, and rectal NETs, a multidisciplinary team should discuss the option to perform an additional resection using more advanced techniques (e.g. ESD or endoscopic full-thickness resection after EMR) on a case-by-case basis. This step should be taken due to insufficient scientific evidence demonstrating a clear relationship between an incomplete resection and a worse clinical outcome.

Declaration of interests

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Additional information

Funding

This paper was funded by Sapienza Università di Roma (RM12218161A53B1D).