Efficacy of endoscopic mucosal resection versus endoscopic submucosal dissection for rectal neuroendocrine tumors ≤10mm: a systematic review and meta-analysis

Current status of endoscopic resection for small rectal neuroendocrine tumors

Rectal neuroendocrine tumor (rNET) is an indolent malignancy often detected during colonoscopy screening. The incidence of rNET has increased approximately 10-fold over the past 30 years. Most rNETs detected during screening endoscopy are small, measuring < 10 mm. Current guidelines recommend endoscopic resection for small, well-differentiated rNET using modified endoscopic submucosal resection (mEMR) or endoscopic submucosal dissection. However, the optimal endoscopic treatment method remains uncertain. This paper summarizes the evidence on mEMR with submucosal stretching, mEMR without submucosal stretching, endoscopic submucosal dissection and endoscopic full-thickness resection. Given that rNETs often exhibit submucosal invasion, achieving adequate resection depth is crucial to ensure histological complete resection. mEMR with submucosal stretching appears favorable due to its high rate of histological complete resection, safety and convenience. Risk factors associated with lymph node and distant metastases are also discussed. A treatment algorithm is proposed to facilitate clinical decision-making.

A rare case of a rectal neuroendocrine neoplasm growing within a lipoma with ulcerative lesions

Neuroendocrine neoplasms (NENs) are a heterogeneous group of tumors with different immunophenotypes, morphological features, clinical presentations, and outcomes. Therefore, the diversity of NENs can easily confuse clinicians and lead to misdiagnosis. This article reports a case of a rectal NEN (r-NEN) growing within a lipoma with ulcerative lesions, which had been mistaken for rectal cancer. Fortunately, an experienced surgeon questioned the initial diagnosis (rectal cancer) after combining the results of a colonoscopic biopsy and the digital anorectal examination, thus enabling the patient to avoid unnecessary surgery. Through the review of this case and relevant literature, we further analyze the growth pattern of NENs and lipomas. Additionally, we hope to enhance clinicians' awareness of a NEN that grew insidiously within a lipoma with surface ulcerative lesions, to make accurate diagnoses and treatments in time.

An Update on the Management of Rectal Neuroendocrine Neoplasms

OPINION STATEMENT

Rectal neuroendocrine neoplasms (NENs) are increasing in incidence. Most lesions are low grade, well-differentiated neuroendocrine tumours with good long term outcomes. However there is metastatic potential and resection offers the only option for a cure and in most cases should be offered to reduce the risk of metastases. Careful staging of rectal NENs should be performed prior to consideration of resection in order to ensure the appropriate technique is chosen, and reduce the risk of incomplete resection. Resection can be endoscopic or surgical, and selecting the appropriate resection technique relies on tumour characteristics such as size, grade, invasion into the muscularis propria, presence of lymph node involvement or of distal metastases. Some patients may require systemic therapies which may involve somatostatin analogues (SSAs), everolimus, tyrosine kinase inhibitors (TKIs), chemotherapy or peptide receptor radionuclide therapy (PRRT). Due the rarity of these tumours, much of the evidence is based on retrospective reviews or smaller cohort studies. This article is an update of the current evidence available to guide management.

Endoscopic management of gastric, duodenal and rectal NETs: Position paper from the Italian Association for Neuroendocrine Tumors (Itanet), Italian Society of Gastroenterology (SIGE), Italian Society of Digestive Endoscopy (SIED)

The present paper reflects the position of the Italian Association for Neuroendocrine Tumors (Itanet), the Italian Society of Gastroenterology (SIGE), and the Italian Society of Digestive Endoscopy (SIED) regarding the management of patients affected by gastric, duodenal, and rectal neuroendocrine neoplasms (NENs) amenable to endoscopic treatment. The key questions discussed in this paper are summarized in Table 1. Data were extracted from the MEDLINE database through searches; expert opinions and recommendations are provided in accordance with the available scientific evidence and the authors' expertise. Recommendations are presented alongside a level of evidence and grade of recommendation based on the GRADE system. This paper specifically focuses on subgroups of NENs considered suitable for endoscopic management according to current international guidelines: i. well-differentiated gastric neuroendocrine tumors (gNET) type 1 < 2 cm and selected cases of type 3; ii. well-differentiated duodenal, non-functioning, non-ampullary NET with size < 2 cm; and well-differentiated rectal NET with size < 2 cm.

Endoscopic treatments for rectal neuroendocrine tumors: a systematic review and network meta-analysis

BACKGROUND

Conventional endoscopic mucosal resection (cEMR), EMR with a transparent cap, EMR using a ligation device (EMR-L), EMR after circumferential precutting (EMR-P), and endoscopic submucosal dissection (ESD) have been used for resecting rectal neuroendocrine tumors (r-NETs). However, there is no consensus regarding which is the best treatment. This study aimed to compare the outcomes of the aforementioned 5 techniques for resecting r-NETs by network meta-analysis.

METHODS

Electronic databases (PubMed, Cochrane Library, Embase, Ovid Medline, and Web of Science) were systematically searched to include relevant studies published from inception to September 1, 2023. The en bloc resection rate, histologic complete resection rate, positive lateral margin rate, positive vertical margin rate, adverse events rate, and procedure time were compared.

RESULTS

A total of 27 studies with a total of 2112 r-NETs were included, and the mean diameter of tumors was 6.24 mm. Pairwise meta-analysis showed that EMR-L and ESD had higher en bloc resection and histologic complete resection rates and lower positive vertical margin rate than those of cEMR in resecting r-NETs. Compared with ESD, EMR-L and EMR-P achieved similar resection rates and significantly shortened the procedure time without increasing adverse events. The network meta-analysis evaluated the surface under the cumulative ranking curves and revealed that EMR-L was the best modality for treating r-NETs considering the comprehensive results of the en bloc resection rate, histologic complete resection rate, positive lateral margin rate, positive vertical margin rate, adverse events rate, and procedure time.

CONCLUSION

EMR-L should be recommended as the first-line endoscopic treatment for small r-NETs.