Current Consensus on I-131 MIBG Therapy

Abstract

Metaiodobenzylguanidine (MIBG) is structurally similar to the neurotransmitter norepinephrine and specifically targets neuroendocrine cells including some neuroendocrine tumors. Iodine-131 (I-131)-labeled MIBG (I-131 MIBG) therapy for neuroendocrine tumors has been performed for more than a quarter-century. The indications of I-131 MIBG therapy include treatment-resistant neuroblastoma (NB), unresectable or metastatic pheochromocytoma (PC) and paraganglioma (PG), unresectable or metastatic carcinoid tumors, and unresectable or metastatic medullary thyroid cancer (MTC). I-131 MIBG therapy is one of the considerable effective treatments in patients with advanced NB, PC, and PG. On the other hand, I-131 MIBG therapy is an alternative method after more effective novel therapies are used such as radiolabeled somatostatin analogs and tyrosine kinase inhibitors in patients with advanced carcinoid tumors and MTC. No-carrier-aided (NCA) I-131 MIBG has more favorable potential compared to the conventional I-131 MIBG. Astatine-211-labeled meta-astatobenzylguanidine (At-211 MABG) has massive potential in patients with neuroendocrine tumors. Further studies about the therapeutic protocols of I-131 MIBG including NCA I-131 MIBG in the clinical setting and At-211 MABG in both the preclinical and clinical settings are needed.

Keywords: Carcinoid tumors; Iodine-131 metaiodobenzylguanidine; Medullary thyroid cancer; Neuroblastoma; Paraganglioma; Pheochromocytoma.

Fig. 1

A 57-year-old female with metastatic paraganglioma receives three cycles of I-131 MIBG therapy. Each dose is 7.4 GBq (200 mCi). A left supraclavicular lymph node metastasis, multiple para-aortic lymph node metastases, bilateral lung metastases, and a right femur metastasis are detected with I-123 MIBG scintigram before the first therapy (a black arrows). I-123 MIBG scintigram after the third therapy shows decreasing uptakes in all lesions (b). Plain CT images before the first therapy (c) and after the third therapy (d) show decrease in size of a para-aortic lymph node swelling (white arrows)