THE TREATMENT OF MALIGNANT METAIODOBENZYLGUANIDINE (I-131-MIBG) - A COMPREHENSIVE REVIEW OF 116 REPORTED PATIENTS

Iiodine-131 metaiodobenzylguanidine (I-131-MIBG), a radiopharmaceutica l 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 experien ce together with the published experience of 23 other centers in 10 co untries, regarding the use of I-131-MIBG for treating patients with ma lignant adrenal pheochromocytomas or extra-adrenal paragangliomas. The re were a total of 116 evaluable patients: 3 were from our current rep ort and another 113 were reported in the literature from 1983 to 1996. A majority of the patients were selected for treatment based upon pos itive tracer uptake studies, The cumulative dose of I-131-MIBG adminis tered ranged from 96 to 2,322 mCi (3.6 to 85.9 GBq), with a mean (+/-S D) of 490+/-350 mCi (18.1+/-13.0 GBq). The subjects received a mean si ngle therapy dose of 158 mCi (5.8 GBq) and the number of doses adminis tered ranged from 1 to 11, with a mean of 3.3+/-2.2 doses. Initial sym ptomatic improvement was achieved in 76% of patients, tumor responses in 30%, and hormonal responses in 45%. Five patients had complete tumo r and hormonal responses, ranging from 16 to 58 months, which were sus tained at the time of reporting. Patients with metastases to soft tiss ue had more favorable responses to treatment than those with metastase s to bone. No difference was noted in the age between the responders a nd non-responders. Adverse effects, recorded in 41% of the treated pat ients, were generally mild except for one fatality from bone marrow ap lasia. Among 89 patients with follow-up data, 45% of the responders ha d 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-responder s, 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 thera py may be a useful palliative adjunct in selected patients with malign ant pheochromocytoma or paraganglioma. Although controlled studies are lacking, our review raises the hope that this therapeutic modality ma y prolong survival with an occasional sustained complete remission or possible cure. (C) 1997, Editrice Kurtis.