131I-metaiodobenzylguanidine therapy of neuroblastoma and other neuroendocrine tumors.

Treatment with (131)I-metaiodobenzylguanidine (MIBG) has been introduced to the management of neuroendocrine tumors (NET) nearly 30 years ago. It provides efficient internal radiotherapy of chromaffin tumors (neuroblastoma, pheochromocytoma, and paraganglioma), but also of carcinoid and other less frequent tumors. Although for various NET types the role of this treatment form decreased by the emergence of peptide receptor radionuclide therapy, (131)I-MIBG still remains the primary radiopharmaceutical for targeting chromaffin tumors with outstanding efficiency. Results in neuroblastoma with overall response rates around 30% in refractory or recurrent diseases have been improved by combinations with chemotherapy, radiosensitizers, and autologous stem cell support. For adult chromaffin tumors, that is, pheochromocytoma and/or paraganglioma, (131)I-MIBG therapy is currently the most efficient nonsurgical therapeutic modality and applies for inoperable, disseminated disease. The antisecretory effect with powerful palliation of symptomatic disease (response rate: 75%-90%) should also be considered when judging treatment benefit. The results in carcinoid tumors are less pronounced, primarily achieving arrest of tumor growth, and most importantly effective functional control. With the presence of peptide receptor radionuclide therapy, (131)I-MIBG remains the alternative radionuclide in this tumor entity, for example, for patients with renal impairment. Another worthwhile mentioning indication-although less prevalent-are metastatic medullary thyroid carcinomas, especially if functioning. These patients are good candidates for this treatment form in the absence of reasonable surgical options and presence of diagnostic MIBG uptake. This article outlines the current status, results, and methodological improvements of (131)I-MIBG therapy.