131I-Metaiodobenzylguanidine therapy in children with advanced neuroblastoma.

Neuroblastoma is an aggressive childhood cancer, with a propensity for early widespread metastasis. Approximately 90% of tumors accumulate the norepinephrine analogue metaiodobenzylguanidine (MIBG) avidly, allowing the use of radiolabeled MIBG for targeted imaging and radiotherapy. After preclinical studies demonstrated activity of 131I-MIBG in models of neuroblastoma, clinical development of this agent ensued. Early clinical trials of 131I-MIBG in patients with relapsed or refractory neuroblastoma defined the toxicity profile of this agent, with myelosuppression as the main dose-limiting toxicity. Subsequent trials defined the activity of 131I-MIBG, with response rates of 20-40% in patients with relapsed or refractory disease. More recent clinical trials have tested 131I-MIBG in combination with chemotherapy or as a component of myeloablative therapies. Given the documented activity of 131I-MIBG, future studies will need to evaluate the impact of radiation sensitizers on this activity and define the role of this agent in treating patients with newly diagnosed high-risk neuroblastoma.