The incremental benefit of functional imaging in pheochromocytoma/paraganglioma: a systematic review

Computed tomography (CT) and magnetic resonance imaging (MRI) are the major imaging modalities used for the localization of catecholamine-producing tumors (pheochromocytoma and paraganglioma). Functional imaging (FI) offers an alternative approach to localize, evaluate, and stage these tumors. Our objective was to describe the additive benefit of FI studies for patients with pheochromocytoma and paraganglioma (PPG) who have undergone MRI or CT scan evaluation. We searched MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and Scopus from database inception through June 2012 for studies that included patients with biochemically proven PPGs who underwent CT or MRI and additional FI for the localization of PPGs. We included 32 studies enrolling a total of 1,264 patients with a mean age of 43-years old. The studies were uncontrolled and evaluated six FI modalities. FI tests provided small additive value to CT/MRI, aiding in the localization of only 24/1,445 primary cases (1.4 %) and 28/805 metastatic cases (3.5 %). In metastatic cases, 6-[F-18]fluoro-L-dihydroxyphenylalanine (DOPA) and fluorodopamine-PET (FDA) were the FI tests most successful at identifying disease missed by CT/MRI, providing additional benefit in 6/60 (10 %) and 5/78 (6.4 %) cases, respectively. No clinically significant findings were observed in any of the predefined subgroups. No study evaluated the impact of FI on the completeness of surgical resection or other patient-important outcomes. Observational evidence suggests that FI tests have a limited additional role in patients with PPGs who have undergone CT/MRI evaluation. However, the role of FI tests in specific subgroups of patients with atypical presentations (metastatic, extra-adrenal) as well as the use of hybrid FI tests should be explored. Further research should also evaluate the impact of FI tests on patient-important outcomes.