Neuroendocrine gastrointestinal tumors - A condensed overview of diagnosis and treatment

Abstract

Neuroendocrine gut and pancreatic tumors are rather rare malignant diseases which has gained increased attraction through the last decennium, possibly through development of new diagnostic and therapeutic methods. Histopathology demonstrating the common neuroendocrine features of these tumors has been the diagnostic corner stone for long, but today it should be suppled with information about the tumor biology. An excellent biochemical marker which is easy to analyze in serum or plasma is chromogranin A, which is a gycoprotein that is stored and released from neuroendocrine cells. This marker can be used for diagnosis and follow-up of the patients. Somatostatin receptor scintigraphy has been one of the most important diagnostic tools for staging of the disease and also indicating sensitivity to treatment with somatostatin analogues. It is a general agreement that almost every patient should be subjected to this procedure before or during the treatment course. From the therapeutic point of view, surgery is nowadays more extensive aiming at reducing the tumor mass in patients who could not be cured by surgery alone. Other means of tumor reduction is liver dearterialization by embolization with starch spheres. The medical treatment of neuroendocrine tumors has made a real break through with the introduction of somatostatin analogues, particularly octreotide, and today most of the hormonally related symptoms can be controlled by this kind of treatment. Somatostatin analogues have also shown to be inhibitors of tumor growth and the latest development is tumor targeted radioactive treatment with Ytrium or Indium labelled octreotide. Long-acting formulation of somatostatin analogues have come into clinical use and significantly improved quality of life for patients with neuroendocrine tumors. Other means of medical treatment are alpha interferons, which have shown particular effect in patients with midgut carcinoid tumors giving both biochemical and tumor responses. Chemotherapy such as streptozotocin plus 5-fluorouracil (5-FU) or doxorubicin is still considered as first-line treatment in malignant endocrine pancreatic tumors but is combined with concomitant somatostatin analogue treatment. In the future a multimodal treatment will further develop combining different agents and also somatostatin receptor subtype specific analogues will come into clinical use.