Metaiodobenzylguanidine (mIBG) and neuroblastoma

Neuroblastoma is the most common extracranial solid tumor in childhood, arising in the sympathetic nervous system, metastatic in half of the patients at diagnosis, with bone and bone marrow as the most frequent sites involved. Most neuroblastomas express the noradrenalin transporter molecule and take up metaiodobenzylguanidine (mIBG), providing a sensitive and specific method of assessing primary tumor and metastatic sites (soft tissue, bone marrow, and bone) when labeled with iodine-123, both at diagnosis, for staging, and as a prognostic factor for evaluation of response to therapy, especially when a semiquantitative scoring method is used. mIBG labeled with iodine-131 has demonstrated activity for targeted therapy of neuroblastoma in both relapsed and newly diagnosed patients, and is being used in clinical trials to optimize treatment of high-risk patients.