Gastroenteropancreatic neuroendocrine tumors: new insights in the diagnosis and therapy.
Summary of "Gastroenteropancreatic neuroendocrine tumors: new insights in the diagnosis and therapy."
Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are relatively rare and heterogenous malignancies. Recent advances in histopathological classification according to the anatomical site of origin, proliferation rate, and extend of the disease have created a valid and powerful tool for the prognostic stratification of GEP-NETs. Chromogranin A is still the best available marker used for the biochemical confirmation of these tumors, but new more sensitive markers are urgently required. Although scintigraphy with (111)In-octreotide has widely been applied for the localization and staging of GEP-NETs, newer imaging modalities based on the functional characteristics of these tumors are evolving aiming not only to facilitate the diagnosis but also prognosis and evaluation of treatment. Somatostatin receptors are the primary therapeutic targets through somatostatin analogs and peptide receptor radionuclide therapy (PRRT) producing symptomatic, biochemical and to a lesser extent antiproliferative effects. Due to the relatively limited and erratic response to chemotherapy, new molecular targeted therapies exploiting some of the biological properties of GEP-NETs such as increased vascularity and inhibition of pathways involved in downstream signal transduction have evolved. Some of these therapies, the mTOR inhibitor everolimus and the tyrosine kinase inhibitor sunitinib, have been recently validated in phase III studies producing practice changing outcomes. In addition, two oral chemotherapeutic agents temozolomide and capecitabine, show promising effects and may replace streptozotocin-based regimens whereas combination therapies with the angiogenesis inhibitor bevacizumab are being investigated. Although progression free survival is used as a feasible primary end point due to the long survival of patients even in the presence of extensive disease prolongation of overall survival following the introduction of new therapies needs to be established.
Department of Pathophysiology, National University of Athens, Mikras Asias 75, 11527, Athens, Greece.
This article was published in the following journal.
- PubMed Source: http://www.ncbi.nlm.nih.gov/pubmed/22124940
- DOI: http://dx.doi.org/10.1007/s12020-011-9562-2
Medical and Biotech [MESH] Definitions
Tumors whose cells possess secretory granules and originate from the neuroectoderm, i.e., the cells of the ectoblast or epiblast that program the neuroendocrine system. Common properties across most neuroendocrine tumors include ectopic hormone production (often via APUD CELLS), the presence of tumor-associated antigens, and isozyme composition.
A group of carcinomas which share a characteristic morphology, often being composed of clusters and trabecular sheets of round "blue cells", granular chromatin, and an attenuated rim of poorly demarcated cytoplasm. Neuroendocrine tumors include carcinoids, small ("oat") cell carcinomas, medullary carcinoma of the thyroid, Merkel cell tumor, cutaneous neuroendocrine carcinoma, pancreatic islet cell tumors, and pheochromocytoma. Neurosecretory granules are found within the tumor cells. (Segen, Dictionary of Modern Medicine, 1992)
A 38-kDa integral membrane glycoprotein of the presynaptic vesicles in neuron and neuroendocrine cells. It is expressed by a variety of normal and neoplastic neuroendocrine cells and is therefore used as an immunocytochemical marker for neuroendocrine differentiation in various tumors. In ALZHEIMER DISEASE and other dementing disorders, there is an important synapse loss due in part to a decrease of synaptophysin in the presynaptic vesicles.
Neuroendocrine Secretory Protein 7b2
An acidic protein found in the NEUROENDOCRINE SYSTEM that functions as a molecular chaperone for PROPROTEIN CONVERTASE 2.
Preliminary cancer therapy (chemotherapy, radiation therapy, hormone/endocrine therapy, immunotherapy, hyperthermia, etc.) that precedes a necessary second modality of treatment.
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