Localization and treatment of familial malignant nonfunctional paraganglioma with iodine-131 MIBG: report of two cases.

Two cases of familial, malignant, nonfunctional paraganglioma are reported. Uptake of iodine-131 metaiodobenzylguanidine ([131I]MIBG) by the tumors and metastases was demonstrated. In the first case, with multicentric and locally invasive disease, [131I]MIBG correctly localized a right carotid body paraganglioma which had been missed arteriographically. In the second case, with widespread, symptomatic metastatic disease, a therapeutic dose of [131I]MIBG produced palliation of bone pain after the failure of radio- and chemotherapy. Uptake of [131I]MIBG by paragangliomas does not correlate with catecholamine secretory activity. Iodine-131 MIBG should be considered as a therapeutic option in unresectable, malignant paragangliomas which take up this radiopharmaceutical.