Proposed MIBG Scan-Based Tumor Response Criteria of High-Specific-Activity I-131-MIBG Therapy in Metastatic Pheochromocytoma/Paraganglioma

High-specific-activity I-131-MIBG (Azedra) is the only Food and Drug Administration-approved therapy for metastatic pheochromocytomas and paragangliomas, which are rare neuroendocrine tumors with limited treatment options. Based on our experience, we proposed here functional imaging-based tumor response criteria for these patient cohorts. Each response category was illustrated with typical sample cases, and clinical correlation was provided.