title: 18F-fluorodihydroxyphenylalanine PET/CT in patients with neuroendocrine tumors of unknown origin: relation to tumor origin and differentiation.
abstract: This work was performed to evaluate the performance of (18)F-fluorodihydroxyphenylalanine ((18)F-FDOPA) PET/CT in detecting primary neuroendocrine tumors (NETs) occult on morphologic and functional imaging, in relation to tumor origin and differentiation.
  
  
  METHODS
  A retrospective study of NET patients who were investigated with (18)F-FDOPA PET/CT imaging in 2 academic endocrine tumor centers was conducted. Only patients with negative conventional and somatostatin receptor scintigraphy (SRS) results were studied.
  
  
  RESULTS
  Twenty-seven patients were evaluated with (18)F-FDOPA PET/CT, 23 at their initial staging and 4 during their follow-up. The primary occult NET was localized by (18)F-FDOPA PET/CT in 12 patients (overall sensitivity, 44%; 52% in patients evaluated at initial diagnosis), leading to tumor resection in all cases. The primary tumors were distributed and graded as follows: 1 duodenum G2 lesion, 7 ileum G2 lesions, 2 terminal ileum G1 lesions, 1 pancreas G2 lesion, and 1 gallbladder G3 lesion. Patients with positive (18)F-FDOPA PET/CT results had higher values of serum chromogranin A (100% vs. 20%, P = 0.0003), serotonin, or urinary 5-hydroxyindolacetic acid (83% vs. 20%, P = 0.003). Two false-negative results were related to poorly differentiated duodenal and prostatic NETs (G3). (18)F-FDOPA PET/CT showed more metastatic anatomic regions than SRS in 17 patients.
  
  
  CONCLUSIONS
  (18)F-FDOPA PET appears to be a sensitive functional imaging tool for the detection of primary NETs occult on SRS, especially tumors with a well-differentiated pattern and serotonin secretion.
authors.affiliation: Biophysics and Nuclear Medicine, Hautepierre University Hospital, Strasbourg, France.
authors.forename: Alessio
authors.initials: A
authors.lastname: Imperiale
authors.forename: Edmond
authors.initials: E
authors.lastname: Rust
authors.forename: Sophie
authors.initials: S
authors.lastname: Gabriel
authors.forename: Julien
authors.initials: J
authors.lastname: Detour
authors.forename: Bernard
authors.initials: B
authors.lastname: Goichot
authors.forename: Bernard
authors.initials: B
authors.lastname: Duclos
authors.forename: Jean-Emmanuel
authors.initials: JE
authors.lastname: Kurtz
authors.forename: Philippe
authors.initials: P
authors.lastname: Bachellier
authors.forename: Izzie-Jacques
authors.initials: IJ
authors.lastname: Namer
authors.forename: David
authors.initials: D
authors.lastname: Taïeb
mesh_terms: D000328:Adult; D000368:Aged; D015331:Cohort Studies; D004295:Dihydroxyphenylalanine / Q000031:analogs & derivatives*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D009362:Neoplasm Metastasis; D018358:Neuroendocrine Tumors / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology*; D049268:Positron-Emission Tomography; D017481:Receptors, Somatostatin / Q000378:metabolism; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed
chemical_list: D017481:Receptors, Somatostatin; C043437:fluorodopa F 18; D004295:Dihydroxyphenylalanine
keywords: 18F-FDOPA; PET/CT; neuroendocrine; somatostatin receptor scintigraphy; unknown primary tumor