Radioiodinated MIBG in paraganglioma and pheochromocytoma: previous results and early experiences using no-carrier-added MIBG

Abstract

The majority of pheochromocytomas and paragangliomas are benign, with malignancy occurring in approximately 10% of pheochromocytoma patients. The malignancy rate among paragangliomas is 15–35% or higher if associated with succinate dehydrogenase B gene mutations. The 5-year mortality rate in malignant pheochromocytoma and paraganglioma is nearly 50%. Malignancy of both pheochromocytoma and paraganglioma is determined by the existence of metastasis or local invasion and not by the cellular characteristics. There are no known clinical, biochemical or histopathological differences between pheochromocytoma and paraganglioma. Metaiodobenzylguanidine (MIBG) radiolabeled with either 123 I or 131 I has been used to diagnose neuroendocrine tumors such as paraganglioma and pheochromocytoma, and 131 I-MIBG has been used to treat these tumors. The role of radioiodinated MIBG in treating neuroendocrine tumors is still being evaluated. More recently, no-carrier-added (nca) MIBG has become available, and the advantages of nca MIBG over ca MIBG are being demonstrated. This article reviews the biology of paragangliomas and pheochromocytomas, the role of MIBG imaging in the diagnosis of these tumors and the role of both ca and nca 131 I-MIBG in the treatment of these tumors. New data on nca 131 I-MIBG in the therapy of these tumors are included.