title: 68Ga-DOTA-Tyr3-octreotide PET in neuroendocrine tumors: comparison with somatostatin receptor scintigraphy and CT.
abstract: The aim of this study was to evaluate the diagnostic value of a new somatostatin analog, (68)Ga-labeled 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid-d-Phe(1)-Tyr(3)-octreotide ((68)Ga-DOTA-TOC), for PET in patients with known or suspected neuroendocrine tumors. PET was compared with conventional scintigraphy and dedicated CT.
  
  
  METHODS
  Eighty-four patients (48 men, 36 women; age range, 28-79 y; mean age +/- SD, 58.2 +/- 12.2 y) were prospectively studied. For analysis, patients were divided into 3 groups: detection of unknown primary tumor in the presence of clinical or biochemical suspicion of neuroendocrine malignancy (n = 13 patients), initial tumor staging (n = 36 patients), and follow-up after therapy (n = 35 patients). Each patient received 100-150 MBq (68)Ga-DOTA-TOC. Imaging results of PET were compared with (99m)Tc-labeled hydrazinonicotinyl-Tyr(3)-octreotide ((99m)Tc-HYNIC-TOC) and (111)In-DOTA-TOC. CT was also performed on every patient using a multidetector scanner. Each imaging modality was interpreted separately by observers who were unaware of imaging findings before comparison with PET. The gold standard for defining true-positive (TP), true-negative (TN), false-positive (FP), and false-negative (FN) results was based on all available histologic, imaging, and follow-up findings.
  
  
  RESULTS
  PET was TP in 69 patients, TN in 12 patients, FP in 1 patient, and FN in 2 patients, indicating a sensitivity of 97%, a specificity of 92%, and an accuracy of 96%. The FP finding was caused by enhanced tracer accumulation in the pancreatic head, and the FN results were obtained in patients with a tumor of the gastrointestinal tract displaying liver metastases. (68)Ga-DOTA-TOC showed higher diagnostic efficacy compared with SPECT (TP in 37 patients, TN in 12 patients, FP in 1 patient, and FN in 34 patients) and diagnostic CT (TP in 41 patients, TN in 12 patients, FP in 5 patients, and FN in 26 patients). This difference was of statistical significance (P < 0.001). However, the combined use of PET and CT showed the highest overall accuracy.
  
  
  CONCLUSIONS
  (68)Ga-DOTA-TOC PET shows a significantly higher detection rate compared with conventional somatostatin receptor scintigraphy and diagnostic CT with clinical impact in a considerable number of patients.
authors.affiliation: Department of Nuclear Medicine, Innsbruck Medical University, Innsbruck, Austria. michael.gabriel@i-med.ac.at
authors.forename: Michael
authors.initials: M
authors.lastname: Gabriel
authors.forename: Clemens
authors.initials: C
authors.lastname: Decristoforo
authors.forename: Dorota
authors.initials: D
authors.lastname: Kendler
authors.forename: Georg
authors.initials: G
authors.lastname: Dobrozemsky
authors.forename: Dirk
authors.initials: D
authors.lastname: Heute
authors.forename: Christian
authors.initials: C
authors.lastname: Uprimny
authors.forename: Peter
authors.initials: P
authors.lastname: Kovacs
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Von Guggenberg
authors.forename: Reto
authors.initials: R
authors.lastname: Bale
authors.forename: Irene J
authors.initials: IJ
authors.lastname: Virgolini
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D005710:Gallium Radioisotopes / Q000493:pharmacokinetics*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015282:Octreotide / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000493:pharmacokinetics; D049268:Positron-Emission Tomography / Q000379:methods; D011446:Prospective Studies; D011877:Radionuclide Imaging / Q000379:methods*; D017481:Receptors, Somatostatin / Q000378:metabolism*; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014443:Tyrosine / Q000737:chemistry*
chemical_list: D005710:Gallium Radioisotopes; D017481:Receptors, Somatostatin; D014443:Tyrosine; D015282:Octreotide; C106246:Edotreotide