title: Direct comparison of (68)Ga-DOTA-TOC and (18)F-FDG PET/CT in the follow-up of patients with neuroendocrine tumour treated with the first full peptide receptor radionuclide therapy cycle.
abstract: OBJECTIVE
  To determine the value of (68)Ga-DOTA-TOC and (18)F-FDG PET/CT for initial and follow-up evaluation of patients with neuroendocrine tumour (NET) treated with peptide receptor radionuclide therapy (PRRT).
  
  
  METHODS
  We evaluated 66 patients who had histologically proven NET and underwent both PRRT and three combined (68)Ga-DOTA-TOC and (18)F-FDG PET/CT studies. (68)Ga-DOTA-TOC PET/CT was performed before PRRT, 3 months after completion of PRRT and after a further 6 - 9 months. (18)F-FDG PET/CT was done within 2 months of (68)Ga-DOTA-TOC PET/CT. Follow-up ranged from 11.8 to 80.0 months (mean 34.5 months).
  
  
  RESULTS
  All patients were (68)Ga-DOTA-TOC PET-positive initially and at follow-up after the first full PRRT cycle. Overall, 62 of the 198 (18)F-FDG PET studies (31 %) were true-positive in 38 of the 66 patients (58 %). Of the 66 patients, 28 (5 grade 1, 23 grade 2) were (18)F-FDG-negative initially and during follow-up (group 1), 24 (5 grade 1, 13 grade 2, 6 grade 3) were (18)F-FDG-positive initially and during follow-up (group 2), 9 patients (2 grade 1, 6 grade 2, 1 grade 3) were (18)F-FDG-negative initially but (18)F-FDG-positive during follow-up (group 3), and 5 patients (all grade 2) were (18)F-FDG-positive initially but (18)F-FDG-negative during follow-up (group 4).(18)F-FDG PET showed more and/or larger metastases than (68)Ga-DOTA-TOC PET in five patients of group 2 and four patients of group 3, all with progressive disease. In three patients with progressive disease who died during follow-up tumour SUVmax increased by 41 - 82 % from the first to the last follow-up investigation.
  
  
  CONCLUSIONS
  In NET patients, the presence of (18)F-FDG-positive tumours correlates strongly with a higher risk of progression. Initially, patients with (18)F-FDG-negative NET may show (18)F-FDG-positive tumours during follow-up. Also patients with grade 1 and grade 2 NET may have (18)F-FDG-positive tumours. Therefore, (18)F-FDG PET/CT is a complementary tool to (68)Ga-DOTA-TOC PET/CT with clinical relevance for molecular investigation.
authors.affiliation: Department of Nuclear Medicine, Innsbruck Medical University, Anichstrasse 35, A-6020, Innsbruck, Austria.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Nilica
authors.affiliation: Department of Nuclear Medicine, Innsbruck Medical University, Anichstrasse 35, A-6020, Innsbruck, Austria.
authors.forename: Dietmar
authors.initials: D
authors.lastname: Waitz
authors.affiliation: Department of Nuclear Medicine, Innsbruck Medical University, Anichstrasse 35, A-6020, Innsbruck, Austria.|Department of Radiology, Innsbruck Medical University, Anichstrasse 35, A-6020, Innsbruck, Austria.
authors.forename: Vlado
authors.initials: V
authors.lastname: Stevanovic
authors.affiliation: Department of Nuclear Medicine, Innsbruck Medical University, Anichstrasse 35, A-6020, Innsbruck, Austria.
authors.forename: Christian
authors.initials: C
authors.lastname: Uprimny
authors.affiliation: Department of Nuclear Medicine, Innsbruck Medical University, Anichstrasse 35, A-6020, Innsbruck, Austria.
authors.forename: Dorota
authors.initials: D
authors.lastname: Kendler
authors.affiliation: Department of Nuclear Medicine, Innsbruck Medical University, Anichstrasse 35, A-6020, Innsbruck, Austria.
authors.forename: Sabine
authors.initials: S
authors.lastname: Buxbaum
authors.affiliation: Department of Nuclear Medicine, Innsbruck Medical University, Anichstrasse 35, A-6020, Innsbruck, Austria.
authors.forename: Boris
authors.initials: B
authors.lastname: Warwitz
authors.affiliation: Department of Nuclear Medicine, Innsbruck Medical University, Anichstrasse 35, A-6020, Innsbruck, Austria.
authors.forename: Llanos
authors.initials: L
authors.lastname: Gerardo
authors.affiliation: Department of Radiology, Innsbruck Medical University, Anichstrasse 35, A-6020, Innsbruck, Austria.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Henninger
authors.affiliation: Department of Nuclear Medicine, Innsbruck Medical University, Anichstrasse 35, A-6020, Innsbruck, Austria.
authors.forename: Irene
authors.initials: I
authors.lastname: Virgolini
authors.affiliation: Department of Nuclear Medicine, Innsbruck Medical University, Anichstrasse 35, A-6020, Innsbruck, Austria. rodriguesradischat@hotmail.com.
authors.forename: Margarida
authors.initials: M
authors.lastname: Rodrigues
mesh_terms: D000328:Adult; D000368:Aged; D001692:Biological Transport; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000378:metabolism; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D018358:Neuroendocrine Tumors / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D015282:Octreotide / Q000031:analogs & derivatives* / Q000378:metabolism; D009942:Organometallic Compounds / Q000378:metabolism; D000072078:Positron Emission Tomography Computed Tomography; D017481:Receptors, Somatostatin / Q000627:therapeutic use*; D012189:Retrospective Studies
chemical_list: C499142:Ga(III)-DOTATOC; D009942:Organometallic Compounds; D017481:Receptors, Somatostatin; D019788:Fluorodeoxyglucose F18; D015282:Octreotide
keywords: 18F-FDG; 68Ga-DOTA-TOC; NET; PET/CT; PRRT