Gastrointestinal neuroendocrine tumors (NETs/NENs) constitute a heterogenous group of malignant disorders including esophageal, gastric, duodenal, small intestinal, colonic, rectal, and appendiceal tumors. In the SEER register, gastroenteropancreatic NETs constitute more than 60% of all NETs with the highest frequency being in the rectum (17.7%), small intestinal (17.3%), and colon (10.1%).
The genetic background of NETs is still not clearly understood. The malignant potential of these tumors ranges from the most benign types of tumors, such as small intestinal tumors (carcinoids) to colonic neuroendocrine carcinoma (NEC) with very malignant behavior, or poorly differentiated small cell neuroendocrine carcinoma.
The mainstay of treatment in low or intermediate grade well-differentiated NETs is surgery, although in some cases less invasive removal of the tumor such as endoscopic resection can be sufficient.
Systemic treatment options include somatostatin analogs such as lanreotide or octreotide, targeted therapy such as everolimus, PRRT, and chemotherapy. So far, immune check point inhibitors have not been shown to have robust activity for the systemic treatment of NET.
Cham: Springer, 2024, 2. p. 175-183