Systemic therapy in the treatment of gastroenteropancreatic neuroendocrine tumors

Neuroendocrine tumors (NET) of the gastrointestinal system represent a group of heterogeneous cancers derived from various endocrine cells located in the stomach, guts and pancreas (GEP). Therapy of GEP NET, due to their biological diversity and different clinical course of each of the tumors, became an interdisciplinary approach with the contribution of a variety of specialists, e.g.: surgeons, endocrinologists, oncologists, nuclear medicine experts, radiologists, and transplantologists. Surgical resection of GEP NET without metastases and limited to one organ is the treatment of choice, because such procedure offers the highest probability of cure. Based on the current evidence in medicine, there is no proof that any adjuvant therapy prolongs disease free- and overall survival. Systemic treatment of GEP NET relies on the application of biological therapy (somatostatin analogs, interferon alfa - IFN alpha) and/or chemotherapy. "Cold" (i.e. unconjugated) somatostatin analogs (SSTA) are the gold standard of management of symptoms in GEP NET. Treatment of GEP NET with IFNa allows similar to SSTA symptomatic and biochemical responses. Chemotherapy using two/three drug combinations (polychemotherapy) gives the best results in the pancreatic NET. In the treatment of midgut carcinoid tumors chemotherapy is less effective.