| Abstract: |
Neuroendocrine tumors (NETs) originate from neuroendocrine cells ubiquitously distributed throughout the body and occur mainly in the gastrointestinal and bronchopulmonary system. They are rare, are mostly sporadic, and comprise 0.66% of all neoplasia. Their incidence/ prevalence is increasing based upon more sophisticated diagnostic strategies. Despite the majority being indolent, they are frequently metastatic at diagnosis. As a consequence their prognosis is often limited. The European Neuroendocrine Tumor Society (ENETS) diagnostic and prognostic stratification criteria are based on histological typing, differentiation, grading (Ki67), and TNM staging. Although the general application of Ki67 is controversial, it remains embedded in therapeutic decision-making pending the implementation of molecular stratification systems. Surgery is the only curative option. It is however effective in ~20% given the metastatic status of most lesions. Other therapeutic options include somatostatin analogs, interferon, "targeted" drugs, and peptide receptor radionuclide radiotherapy (PRRT). NETs present a diagnostic and therapeutic challenge as their clinical presentation is protean, nonspecific, and late with hepatic metastases often present. Imaging plays a fundamental role in diagnosis, staging, treatment selection, and follow-up. Current modalities include morphologic techniques (CT,MRI), transabdominal ultrasound (US), and endoscopic (EUS) and intraoperative US (IOUS). Molecular imaging includes scintigraphy (111In-pentetreotide or 99mTc-HYNIC-Tyr3-octreotide), and, more recently, PET with 68Ga-labeled somatostatin analogs (SSA), 18F-DOPA and [11C]5-HTP; catecholamine metabolism is usually imaged with 123I-metaiodobenzylguanidine. [18F]FDG PET/CT has a prognostic role. A role for somatostatin receptor antagonists (better target/ background ratio) as theranostics is currently proposed. The major unmet needs are the development of more inclusive criteria for therapy monitoring, the validation of the recent PET techniques, and the integration of molecular biologic and metabolic information. © Springer International Publishing Switzerland 2017. All rights reserved. |
