Gastroenteropancreatic neuroendocrine tumors: new insights in the diagnosis and therapy
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REVIEW
Gastroenteropancreatic neuroendocrine tumors: new insights in the diagnosis and therapy Krystallenia I. Alexandraki • Gregory Kaltsas
Received: 2 September 2011 / Accepted: 12 October 2011 / Published online: 29 November 2011 Ó Springer Science+Business Media, LLC 2011
Abstract 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 111In-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 streptozotocinbased regimens whereas combination therapies with the K. I. Alexandraki G. Kaltsas (&) Department of Pathophysiology, National University of Athens, Mikras Asias 75, 11527 Athens, Greece e-mail: [email protected]
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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. Keywords Somatostatin analogs Everolimus Sunitinib Temozolomide
Introduction Neuroendocrine tumors (NETs) constitute a wide range of tumors derived from neuroendocrine cells (NE) that are widely distributed throughout the human body [1]. Although initially their diagnosis was based on the unique ability of tumor cells to incorporate silver salts, it is now based on the immunohistochemical documentation of markers of NE differentiation, mainly chromogranin A (CgA) and synaptophysin [2]. A distinctive feature of these tumors is their capability to synthesise, store, and secrete a number of amines and peptides which can be biologi
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