Role of Advanced Gastrointestinal Endoscopy in the Comprehensive Management of Neuroendocrine Neoplasms

SIMPLE SUMMARY: Neuroendocrine tumors (NET) arise from cells throughout the diffuse endocrine system. They are primarily sporadic but can also occur in the context of genetic syndromes like multiple endocrine neoplasia. They are most commonly seen in the gastrointestinal tract, pancreas, and lungs. Data show that the incidence of NETs is increasing, partly contributed to by improving diagnostic modalities and their increasing use. The management of larger (>2 cm) NETs and those with evidence of local or metastatic involvement is relatively well defined and involves surgery, chemotherapy, or a combination. Endoscopic evaluation is pivotal in diagnosing, staging, and grading NETs. Furthermore, advanced endoscopic techniques like resection and ablation can now successfully treat NETs, particularly those less than 2 cm, potentially reducing the adverse events and healthcare costs associated with surgical management. This article discusses the latest advances in the endoscopic evaluation and management of this rare condition. ABSTRACT: Neuroendocrine neoplasms (NENs), also called neuroendocrine tumors (NETs), are relatively uncommon, heterogenous tumors primarily originating in the gastrointestinal tract. With the improvement in technology and increasing use of cross-sectional imaging and endoscopy, they are being discovered with increasing frequency. Although traditionally considered indolent tumors with good prognoses, some NENs exhibit aggressive behavior. Timely diagnosis, risk stratification, and management can often be a challenge. In general, small NENs without local invasion or lymphovascular involvement can often be managed using minimally invasive advanced endoscopic techniques, while larger lesions and those with evidence of lymphovascular invasion require surgery, systemic therapy, or a combination thereof. Ideal management requires a comprehensive and accurate understanding of the stage and grade of the tumor. With the recent advancements, a therapeutic advanced endoscopist can play a pivotal role in diagnosing, staging, and managing this rare condition. High-definition white light imaging and digital image enhancing technologies like narrow band imaging (NBI) in the newer endoscopes have improved the diagnostic accuracy of traditional endoscopy. The refinement of endoscopic ultrasound (EUS) over the past decade has revolutionized the role of endoscopy in diagnosing and managing various pathologies, including NENs. In addition to EUS-directed diagnostic biopsies, it also offers the ability to precisely assess the depth of invasion and lymphovascular involvement and thus stage NENs accurately. EUS-directed locoregional ablative therapies are increasingly recognized as highly effective, minimally invasive treatment modalities for NENs, particularly pancreatic NENs. Advanced endoscopic resection techniques like endoscopic submucosal dissection (ESD), endoscopic submucosal resection (EMR), and endoscopic full-thickness resection (EFTR) have been increasingly used over the past decade with excellent results in achieving curative resection of various early-stage gastrointestinal luminal lesions including NENs. In this article, we aim to delineate NENs of the different segments of the gastrointestinal (GI) tract (esophagus, gastric, pancreatic, and small and large intestine) and their management with emphasis on the endoscopic management of these tumors.