The treatment of malignant metaiodobenzylguanidine (131I-MIBG):: A comprehensive review of 116 reported patients

Iiodine-131 metaiodobenzylguanidine (I-131-MIBG), a radiopharmaceutical agent used for scintigraphic localization of pheochromocytomas, has been employed to treat malignant pheochromocytomas since 1983 in a few specialized centers around the world. We review our clinical experience together with the published experience of 23 other centers in 10 countries, regarding the use of I-131-MIBG for treating patients with malignant adrenal pheochromocytomas or extra-adrenal paragangliomas. There were a total of 116 evaluable patients: 3 were from our current report and another 113 were reported in the literature from 1983 to 1996. A majority of the patients were selected for treatment based upon positive tracer uptake studies, The cumulative dose of I-131-MIBG administered ranged from 96 to 2,322 mCi (3.6 to 85.9 GBq), with a mean (+/-SD) of 490+/-350 mCi (18.1+/-13.0 GBq). The subjects received a mean single therapy dose of 158 mCi (5.8 GBq) and the number of doses administered ranged from 1 to 11, with a mean of 3.3+/-2.2 doses. Initial symptomatic improvement was achieved in 76% of patients, tumor responses in 30%, and hormonal responses in 45%. Five patients had complete tumor and hormonal responses, ranging from 16 to 58 months, which were sustained at the time of reporting. Patients with metastases to soft tissue had more favorable responses to treatment than those with metastases to bone. No difference was noted in the age between the responders and non-responders. Adverse effects, recorded in 41% of the treated patients, were generally mild except for one fatality from bone marrow aplasia. Among 89 patients with follow-up data, 45% of the responders had relapsed with recurrent or progressive disease after a mean interval of 29.3+/-31.1 months (median 19 months). Of patients with an initial response to I-131-MIBG, death was reported in 33% after a mean of 23.2+/-8.1 months(median 22 months) following treatment. Of non-responders, death was reported in 45% after a mean of 14.3+/-8.3 months (median 13 months). In conclusion, this review suggests that I-131-MIBG therapy may be a useful palliative adjunct in selected patients with malignant pheochromocytoma or paraganglioma. Although controlled studies are lacking, our review raises the hope that this therapeutic modality may prolong survival with an occasional sustained complete remission or possible cure. (C) 1997, Editrice Kurtis.