The diagnostic and therapeutic utility of radioiodinated metaiodobenzylguanidine (MIBG). 5 years of experience.

The authors' experience of more than 5 years in the diagnostic and therapeutic use of radioiodinated MIBG in neural crest tumors is reported. 123I/131I-MIBG scintigraphy was performed in 158 patients: 75 suspected (24 proven) pheochromocytomas (pheos), 43 neuroblastomas (NB), 20 medullary thyroid carcinomas (MTC), 6 ganglioneuromas, 5 carcinoids and 1 insulinoma. Eight cases of tumors not originating from the neural crest were also investigated. The diagnostic sensitivity of the method was above 90% both in pheos and NB (primary tumors and bone metastases). The examination was less effective in localizing MTC (sensitivity = 64.4% in primary or residual/recurrent tumors). The scintigraphic outcome was negative in ganglioneuromas, carcinoids and insulinoma. Specificity was very high (greater than 95%), and no false positive results were found in tumors not deriving from the neural crest. 131I-MIBG treatment was administered to four patients with malignant pheo, nine with NB and four with MTC. Therapy resulted in a complete response in one pheo, two NB and one MTC treated after surgery or at diagnosis (one NB); it gave partial response and prolonged remission in five advanced cases (one pheo, two NB and two MTC); it resulted in temporary stabilization of the disease in one pheo and two NBs; it was ineffective in four cases.