title: Somatostatin receptor PET in neuroendocrine tumours: 68Ga-DOTA0,Tyr3-octreotide versus 68Ga-DOTA0-lanreotide.
abstract: OBJECTIVE
  The aim of this study was to evaluate the impact of (68)Ga-labelled DOTA(0)-lanreotide ((68)Ga-DOTA-LAN) on the diagnostic assessment of neuroendocrine tumour (NET) patients with low to moderate uptake on planar somatostatin receptor (SSTR) scintigraphy or (68)Ga-labelled DOTA(0),Tyr(3)-octreotide ((68)Ga-DOTA-TOC) positron emission tomography (PET).
  
  
  METHODS
  Fifty-three patients with histologically confirmed NET and clinical signs of progressive disease, who had not qualified for peptide receptor radionuclide therapy (PRRT) on planar SSTR scintigraphy or (68)Ga-DOTA-TOC PET (n = 38) due to lack of tracer uptake, underwent (68)Ga-DOTA-LAN PET to evaluate a treatment option with (90)Y-labelled lanreotide according to the MAURITIUS trial. The included patients received 150 ± 30 MBq of each radiopharmaceutical intravenously. PET scans were acquired 60-90 min after intravenous bolus injection. Image results from both PET scans were compared head to head, focusing on the intensity of tracer uptake in terms of treatment decision. CT was used for morphologic correlation of tumour lesions. To further evaluate the binding affinities of each tracer, quantitative and qualitative values were calculated for target lesions.
  
  
  RESULTS
  (68)Ga-DOTA-LAN and (68)Ga-DOTA-TOC both showed equivalent findings in 24/38 patients when fused PET/CT images were interpreted. The sensitivity, specificity and accuracy of (68)Ga-DOTA-LAN in comparison to CT were 0.63, 0.5 and 0.62 (n = 53; p < 0.0001) and for (68)Ga-DOTA-TOC in comparison to CT 0.78, 0.5 and 0.76 (n = 38; p < 0.013), respectively. (68)Ga-DOTA-TOC showed a significantly higher maximum standardized uptake value (SUV(max)) regarding the primary tumour in 25 patients (p < 0.003) and regarding the liver in 30 patients (p < 0.009) compared to (68)Ga-DOTA-LAN. Corresponding values of both PET scans for tumour and liver did not show any significant correlation. (68)Ga-DOTA-TOC revealed more tumour sites than (68)Ga-DOTA-LAN (106 vs 53). The tumour to background ratios for tumour and liver calculated from SUV(max) measurements were significantly higher for (68)Ga-DOTA-TOC than (68)Ga-DOTA-LAN (p < 0.02).
  
  
  CONCLUSIONS
  (68)Ga-DOTA-TOC PET imaging is an established imaging procedure for accurate staging of NET patients. (68)Ga-DOTA-LAN should only be considered as a PET tracer of second choice in patients with no pathologic tracer uptake on (68)Ga-DOTA-TOC PET. In these patients, (68)Ga-DOTA-LAN PET can provide valuable information when evaluating PRRT as the treatment option, as a broader spectrum of human SSTR subtypes can be detected.
authors.affiliation: Department of Nuclear Medicine, Innsbruck Medical University, Anichstraße 35, 6020, Innsbruck, Austria. daniel.putzer@i-med.ac.at
authors.forename: Daniel
authors.initials: D
authors.lastname: Putzer
authors.forename: Alexander
authors.initials: A
authors.lastname: Kroiss
authors.forename: Dietmar
authors.initials: D
authors.lastname: Waitz
authors.forename: Michael
authors.initials: M
authors.lastname: Gabriel
authors.forename: Tatjana
authors.initials: T
authors.lastname: Traub-Weidinger
authors.forename: Christian
authors.initials: C
authors.lastname: Uprimny
authors.forename: Elisabeth
authors.initials: E
authors.lastname: von Guggenberg
authors.forename: Clemens
authors.initials: C
authors.lastname: Decristoforo
authors.forename: Boris
authors.initials: B
authors.lastname: Warwitz
authors.forename: Gerlig
authors.initials: G
authors.lastname: Widmann
authors.forename: Irene Johanna
authors.initials: IJ
authors.lastname: Virgolini
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001692:Biological Transport; D005260:Female; D006573:Heterocyclic Compounds, 1-Ring / Q000378:metabolism; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D018358:Neuroendocrine Tumors / Q000000981:diagnostic imaging* / Q000378:metabolism*; D015282:Octreotide / Q000031:analogs & derivatives* / Q000378:metabolism; D009942:Organometallic Compounds / Q000378:metabolism; D010456:Peptides, Cyclic / Q000378:metabolism; D049268:Positron-Emission Tomography / Q000379:methods*; D017481:Receptors, Somatostatin / Q000378:metabolism*; D012189:Retrospective Studies; D013004:Somatostatin / Q000031:analogs & derivatives* / Q000378:metabolism; D055815:Young Adult
chemical_list: C550726:68Ga-octreotide, DOTA(0)-Tyr(3)-; D006573:Heterocyclic Compounds, 1-Ring; D009942:Organometallic Compounds; D010456:Peptides, Cyclic; D017481:Receptors, Somatostatin; C558148:gallium 68-DOTA-lanreotide; D013004:Somatostatin; D015282:Octreotide