Role of (18)F-FDG PET/CT, (123)I-MIBG SPECT, and CT in Restaging Patients Affected by Malignant Pheochromocytoma.

Objective: Pheochromocytoma (PH) is a rare catecholamine-secreting tumor that arises from chromaffin tissue within the adrenal medulla and extra-adrenal sites; commonly it is sporadic, and malignant PH accounts for about 10% of all cases. Several imaging modalities have been used for the diagnosis and staging of this tumor: functional imaging using radio-labelled metaiodobenzylguanidine and, more recently, (18)F-fluorodeoxyglucose positron emission tomography ((18)F-FDG PET/CT), which offers substantial sensitivity and specificity to correctly detect metastatic PH and helps to identify patients suitable for treatment with radiopharmaceuticals. The aim of our study was to compare CT, (18)F-FDG PET/CT, and (123)I-metaiodobenzylguanidine single photon emission tomography ((123)I-MIBG SPECT) as feasible methods to restage patients diagnosed histologically with PH.

Methods: We retrospectively evaluated 38 patients (27 females and 11 males; mean age: 44 ± 15 years) with malignant PH documented histologically after surgical intervention. These patients underwent CT, (18)F-FDG PET/CT, and (123)I-MIBG SPECT.

Results: (18)F-FDG PET/CT showed positive results for neoplastic tissue in 33/38 patients (86.8%) and negative in 5/38 (13.2%), in concordance with CT alone. (123)I-MIBG SPECT was positive in 30/38 patients (78,9%) and negative in 8/38 (21.1%). No differences in lesion numbers were found between (18)F-FDG PET/CT and CT, whereas a difference could be demonstrated between (18)F-FDG PET/CT and (123)I-MIBG SPECT.

Conclusions: (18)F-FDG PET/CT could more accurately restage patients with PH than CT and (123)I-MIBG SPECT, also in the absence of a staging study.