Diagnostic Performance of ¹²⁴I-Metaiodobenzylguanidine PET/CT in Patients with Pheochromocytoma

^123/131I-metaiodobenzylguanidine (MIBG) scintigraphy has shown a high specificity for imaging pheochromocytoma and paraganglioma, but with low sensitivity because of low spatial resolution. ¹²⁴I-MIBG PET may be able to overcome this limitation and improve the staging of patients with (suspected) pheochromocytoma. Methods: We analyzed the sensitivity, specificity, and positive and negative predictive values of ¹²⁴I-MIBG PET in 43 consecutive patients with suspected (recurrence of) pheochromocytoma using histopathologic (n = 25) and clinical validation (n = 18) as the standard of truth. Furthermore, we compared the detection rate of ¹²⁴I-MIBG PET versus contrast-enhanced (CE) CT on a per-patient and per-lesion basis in 13 additional patients with known metastatic malignant pheochromocytoma. Results:¹²⁴I-MIBG PET/CT was positive in 19 (44%) of 43 patients with suspected pheochromocytoma. The presence of pheochromocytoma was confirmed in 22 (51%) of 43. ¹²⁴I-MIBG PET/CT sensitivity, specificity, and positive and negative predictive values were 86%, 100%, 100%, and 88%, respectively. ¹²⁴I-MIBG PET was positive in 11 (85%) of 13 patients with malignant pheochromocytoma. Combined ¹²⁴I-MIBG PET and CE CT detected 173 lesions, of which 166 (96%) and 118 (68%) were visible on ¹²⁴I-MIBG PET and CE CT, respectively. Conclusion:¹²⁴I-MIBG PET detects pheochromocytoma with high accuracy at initial staging and a high detection rate at restaging. Future assessment of ¹²⁴I-MIBG PET for treatment guidance, including personalized ¹³¹I-MIBG therapy, is warranted.