title: The role of [(18)F]fluorodeoxyglucose positron emission tomography and [(111)In]-diethylenetriaminepentaacetate-D-Phe-pentetreotide scintigraphy in the localization of ectopic adrenocorticotropin-secreting tumors causing Cushing's syndrome.
abstract: Conventional imaging modalities cannot localize the source of ACTH in 30-50% of patients with Cushing's syndrome (CS) caused by ectopic ACTH secretion (EAS). We prospectively evaluated whether [(18)F]fluorodeoxyglucose (FDG) positron emission tomography (PET) or [(111)In]-diethylenetriaminepentaacetate-D-Phe-pentetreotide (OCT) at higher than standard doses of radionuclide (18 mCi; H-OCT), can detect these tumors. Seventeen patients with presumed EAS based on inferior petrosal sinus sampling results underwent routine anatomical imaging studies [computed tomography (CT) and magnetic resonance imaging (MRI)] and OCT scintigraphy with 6 mCi (L-OCT). Research studies included FDG-PET in all patients and H-OCT if L-OCT was negative. ACTH-secreting tumors were localized in 13 patients and were occult in four. Nine of 17 CT, six of 16 MRI, six of 17 FDG-PET, eight of 17 L-OCT, and one of nine H-OCT studies were true positives. The sensitivity of CT and combined H- and L-OCT scintigraphy was higher (both 53%; 95% confidence interval, 29-76%) than that of MRI (37%; 95% confidence interval, 16-64%) or FDG-PET (35%; 95% confidence interval, 15-61%). FDG-PET did not detect tumors that were occult on CT/MRI. L-OCT was a useful complementary modality to CT and MRI. As H-OCT identified a tumor in one patient with otherwise negative imaging, it should be considered only when other imaging modalities fail to localize the ACTH-secreting tumor in patients with EAS.
authors.affiliation: Pediatric and Reproductive Endocrinology Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-1583, USA. karel@mail.nih.gov
authors.forename: Karel
authors.initials: K
authors.lastname: Pacak
authors.forename: Ioannis
authors.initials: I
authors.lastname: Ilias
authors.forename: Clara C
authors.initials: CC
authors.lastname: Chen
authors.forename: Jorge A
authors.initials: JA
authors.lastname: Carrasquillo
authors.forename: Millie
authors.initials: M
authors.lastname: Whatley
authors.forename: Lynnette K
authors.initials: LK
authors.lastname: Nieman
mesh_terms: D000182:ACTH Syndrome, Ectopic; D000328:Adult; D000368:Aged; D003480:Cushing Syndrome / Q000209:etiology*; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007205:Indium Radioisotopes; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000150:complications / Q000175:diagnosis / Q000000981:diagnostic imaging* / Q000378:metabolism*; D004369:Pentetic Acid; D019275:Radiopharmaceuticals; D014055:Tomography, Emission-Computed; D014057:Tomography, X-Ray Computed
chemical_list: D007205:Indium Radioisotopes; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D004369:Pentetic Acid