Interim results of an open-label, single-arm trial of ultratrace I-131-iobenguane in patients with metastatic pheochromocytoma/paraganglioma (Pheo).

e13592 Background: To evaluate the therapeutic efficacy of no carrier added (nca) I-131-MIBG in pheo as measured by > 50% reduction of all antihypertensive medication for ≥ 6 months. Secondarily, to evaluate safety (including radiation absorbed dose to normal organs) and the proportion of subjects with objective response per modified RECIST and biomarker response by change in Chromogranin A (CgA). Methods: Pts with metastatic pheo causing secondary hypertension were treated with up to two 500 mCi doses of 131I-nca-MIBG 3-6 months apart. The administered dose was limited by pretreatment organ dosimetry and normal tissue tolerance estimates of Emami (1991). Response and toxicity were evaluated for a minimum of 1 year. Results: To date, 41 pts (17-72 years) received at least one treatment (full analysis; FA); 34 pts received 2 treatments (per protocol; PP); All patients have been followed at least 1 year or until death. The primary endpoint of sustained reduction in HTN meds was achieved in 32% and 29% of PP...