Repeated Radionuclide therapy in metastatic paraganglioma leading to the highest reported cumulative activity of 131I-MIBG

Targeted radiotherapy with 131I-metaiodobenzylguanidine (131I-MIBG) provides a generally well tolerated treatment in chromaffin tumors; i.e. neuroblastoma, pheochromocytoma, and paraganglioma [1-4]. Hematotoxicity is the primary side effect depending on the administered activity, metastatic bone marrow infiltration and other performed treatment modalities as chemotherapy [5-7]. Treatment protocols mostly use activities between 3.7 and 11.1 GBq (100-300 mCi) per course [8,9]. Newer schedules use 14.8-18.5 GBq (400-500 mCi) per treatment course and high-dose concepts may incorporate an initial dose of > 22,2 GBq (600 mCi) supported by potential autologous stem-cell rescue (ASCR) [10,11].However, there is no existing recommendation for repeat treatment or maximum cumulative activity. While the common total administered activity per patient varies between 10 and 40 GBq [9,12] occasional reports of higher values up to 70 GBq do exist [10,13-16]. One patient with metastatic pheochromocytoma was noted to receive as much as 85.9 GBq (2321 mCi) 131I-MIBG [17].We report on a case of metastatic paraganglioma undergoing repetitive MIBG treatment during the course of disease, resulting in an extraordinary high cumulative activity of 3 Ci without any observed dose limiting toxicity.A 52-year-old female with a highly functional retroperitoneal paraganglioma and previous tumorectomy was referred for 131I-MIBG therapy in recurrent hepatic metastatic disease. The patient suffered from hypertension, tachycardia and sweating. 131I-MIBG therapy was initiated after confirmation of tumor uptake in a diagnostic MIBG scan. The treatment was performed using 11.1 GBq (300 mCi) 131I-MIBG of high specific activity (GE Healthcare, Amersham, Germany), given intravenously by slow infusion. The minimum interval between two courses of 131I-MIBG was eight weeks. Drugs known to interfere with MIBG uptake were discontinued before admission to treatment [18]. Thyroid uptake of free radioiodine was block