Surgery for metastatic pancreatic neuroendocrine tumors: a narrative review.

Background and Objective: Pancreatic neuroendocrine tumors (PanNETs) are derived from the islet cells of the pancreas and have been increasing in incidence. Most of these tumors are nonfunctional although some can secrete hormones and lead to hormone-specific clinical syndromes. Surgery is the mainstay of treatment for localized tumors, however, surgical resection is controversial in metastatic PanNETs. This narrative review seeks to summarize the current literature surrounding surgery, specifically in the controversial area of metastatic PanNETs, review current treatment paradigms, and understand the benefits of surgery in this group of patients. Methods: Authors searched PubMed using the terms "surgery pancreatic neuroendocrine tumor", "metastatic neuroendocrine tumor", and "liver debulking neuroendocrine tumor" from January 1990 to June 2022. Only English language publications were considered. Key Content and Findings: There is no consensus among the leading specialty organizations regarding surgery for metastatic PanNETs. When considering surgery for metastatic PanNETs, tumor grade and morphology, location of the primary tumor, extra-hepatic or extra-abdominal disease, as well as liver tumor burden and metastatic distribution should be considered. Because the liver is the most common site of metastasis and liver failure is the most common cause of death in patients with hepatic metastases, attention is centered here on debulking and other ablative techniques. Liver transplantation is rarely used for hepatic metastases but could be beneficial in a small subset of patients. Retrospective studies have demonstrated improvement in survival and symptoms after surgery for metastatic disease, but the lack of prospective randomized control trials significantly limits analysis of surgical benefits in patients with metastatic PanNETs. Conclusions: Surgery is the standard of care for localized PanNETs, while it remains controversial in metastatic disease. Many studies have shown a survival and symptomatic benefit to surgery and liver debulking in select groups of patients. However, most of the studies on which recommendations are based in this population are retrospective in nature and are subject to selection bias. This presents an opportunity for future investigation.