131I-metaiodobenzylguanidine therapy for malignant pheochromocytoma.

131I-metaiodobenzylguanidine (MIBG) therapy was given to five patients with malignant pheochromocytoma. The patients received 1-3 doses of 3.33-4.625 GBq (total dose: 3.7 to 10.73 GBq). Partial tumor regression was observed in two patients, the tumor was unchanged in two patients, and slow progression was noted in one patient. Marked improvement in clinical symptoms was achieved in four patients. The other patient had no symptoms before 131I-MIBG treatment, but the serum epinephrine and dopamine decreased. There were no severe untoward responses in four patients. However, one patient developed transient but severe orthostatic hypotension, hypertension, and hyperglycemia from 1 week to 1 month after 131I-MIBG administration. Although complete remission was not obtained, all the patients achieved some benefit from 131I-MIBG therapy. Thus, 131I-MIBG appears to be useful for the palliation of malignant pheochromocytoma.