123I-labeled metaiodobenzylguanidine for diagnosis of neuroendocrine tumors

Metaiodobenzylguanidine (MIBG) is an analog of the catecholamine norepinephrine. Through a type I energy-dependent active amine transport mechanism, it is taken up in presynaptic cytoplasmic storage vesicles of adrenergic nerves. Many normal tissues that have rich adrenergic innervation accumulate MIBG, including the heart and salivary glands. Additionally, MIBG is accumulated in benign and malignant tissues derived from the neural crest, such as the adrenal medulla and neuroendocrine tumors (NETs), where it is stored within neurosecretory granules. This provides the molecular basis for highly specific imaging and therapy with radiolabeled MIBG. Both 123 I-MIBG and 131 I-MIBG are available for diagnostic purposes. Considering the physical characteristics of 123 I (159 keV photon energy, 13.2 hours half-life) and clinical experience, 123 I-MIBG is the agent of choice for diagnostic imaging. It shows high sensitivity and specificity in detecting NETs. NETs include a wide range of neoplasms arising from tissues derived from the neural crest, such as neuroblastomas (NBs), pheochromocytomas, paragangliomas, NETs of the gastroenteropancreatic tract (GEP tumors), as well as medullary thyroid carcinomas (MTCs). The purpose of this review is to summarize the diagnostic application of 123 I-MIBG in detecting diverse NETs and in guiding the subsequent clinical management and treatment protocols.