title: Discordant localization of 2-[18F]-fluoro-2-deoxy-D-glucose in 6-[18F]-fluorodopamine- and [(123)I]-metaiodobenzylguanidine-negative metastatic pheochromocytoma sites.
abstract: BACKGROUND
  Although the majority of pheochromocytomas (PHEO) are benign, a subset is malignant. Computed tomography (CT) and magnetic resonance imaging (MRI) localize PHEO with high sensitivity but, because of limited specificity, [(131)I]- or [(123)I]-metaiodobenzylguanidine ([(131)I]- or [(123)I]-MIBG) is often used as a complementary agent. 6-[18F]-fluorodopamine ([18F]-DA) has been developed as a radiopharmaceutical for the targeting of noradrenergic pathways, and has been shown to result in a better detection rate of PHEO sites than MIBG; however, [18F]-DA has shown a lack of accumulation in some patients with metastatic PHEO.
  
  
  METHODS
  Five patients with widespread metastatic PHEO who had CT and MRI evidence of metastatic disease (one man and four women; age range, 25-64 years), and who underwent imaging with [(123)I]-MIBG, [18F]-DA and 2-[18F]-fluoro-2-deoxy-D-glucose ([18F]-FDG), were evaluated retrospectively. Tomographic imaging was performed and positron emission tomography (PET) images were inspected visually and quantitatively.
  
  
  RESULTS
  All five patients had [(123)I]-MIBG scans that grossly underestimated the extent of disease when compared with conventional CT and MRI. All lesions seen on [(123)I]-MIBG scans were detected on [18F]-DA scans, which also detected additional lesions. Nonetheless, [18F]-DA also failed to detect numerous lesions seen on CT and MRI. In all of these cases, [18F]-FDG PET showed lesions that were not detected on either [(123)I]-MIBG or [18F]-DA scans.
  
  
  CONCLUSIONS
  When [(123)I]-MIBG or [18F]-DA fails to localize lesions seen on conventional imaging studies, [18F]-FDG may be recommended as an ancillary test for the diagnosis and localization of metastatic PHEO. This is particularly important in patients with aggressive PHEO.
authors.affiliation: Nuclear Medicine Department, Clinical Center, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-1109, USA.
authors.forename: Marcelo
authors.initials: M
authors.lastname: Mamede
authors.forename: Jorge A
authors.initials: JA
authors.lastname: Carrasquillo
authors.forename: Clara C
authors.initials: CC
authors.lastname: Chen
authors.forename: Pedro
authors.initials: P
authors.lastname: Del Corral
authors.forename: Millie
authors.initials: M
authors.lastname: Whatley
authors.forename: Ioannis
authors.initials: I
authors.lastname: Ilias
authors.forename: Alejandro
authors.initials: A
authors.lastname: Ayala
authors.forename: Karel
authors.initials: K
authors.lastname: Pacak
mesh_terms: D019797:3-Iodobenzylguanidine / Q000493:pharmacokinetics; D000328:Adult; D004298:Dopamine / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D005188:False Negative Reactions; D005260:Female; D005462:Fluorine Radioisotopes / Q000493:pharmacokinetics; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics; D006801:Humans; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics; D008297:Male; D008875:Middle Aged; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity
chemical_list: D005462:Fluorine Radioisotopes; D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D019797:3-Iodobenzylguanidine; C029253:6-fluorodopamine; D004298:Dopamine