[Gastrointestinal neuroendocrine tumors]

Abstract

Two thirds of all neuroendocrine tumors (NET) are located in the gastroentero-pancreatic system. Depending on its localisation, each tumor presents a different histological pattern as well as different clinical symptoms and prognosis. Symptoms are usually due to the mass effects of the local tumor or tumor-related fibrosis. The classical "carcinoid-syndrome" with flush and diarrhea is seen in fewer than 10 %. Tests like chromogranin A (serum) or 5-hydroxyindolacetic acid (24h urine-collection) are indicators for the initial diagnosis of NET. Somatostatin-receptor scintigraphy is the most valuable imaging modality. In addition CT/MRI can be used for further topographical definition. Endoscopic techniques like the use of capsule endoscopy are being evaluated for the diagnosis of small intestinal NETs. The only curative treatment of NET is still complete surgical resection. However, it can only be done in 20 %, depending on localization and local extension of the primary tumor. If the liver is involved local ablation techniques should be considered. The gold standard for medical treatment is the use of somatostatin analogs, although interferons show a comparable therapeutic potential. Traditional cytotoxic agents should only be used for poorly differentiated tumors refractory to other forms of treatment. New compounds that target different pathways at the intra- and intercellular level are under investigation. Supportive therapy should be considered for the control of symptoms.