Surgical treatment of gastrointestinal neuroendocrine tumors

Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are uncommon but clinically challenging and fascinating tumors. GEP-NETs present as either functional or as nonfunctional tumors. Functional tumors are commonly associated with a specific hormonal syndrome directly related to a hormone secreted by the tumor, like gastrinomas with a Zollinger-Ellison syndrome or carcinoid syndrome in patients with neuroendocrine tumors (NET) of the ileum. Nonfunctional tumors do not secrete a hormone resulting in a clinical syndrome. The natural course of GEP-NETs is highly variable. Small, benign neoplasms such as 90% of all insulinomas or gastric endocrine tumors type 1 are readily curable by surgical resection; however, most other GEP-NETs have a much less favorable prognosis. Patients with completely resected tumors generally have a good prognosis, and an aggressive surgical approach in patients with advanced disease may also prolong survival. This review focuses on the current standards of surgical treatment of gastric endocrine tumors, NETs of the pancreas (PNET) and NETs of the ileum. Although the evidence level is low in many instances due to the lack of randomized controlled trials, important treatment recommendations can be given.