title: SUV of [68Ga]DOTATOC-PET/CT Predicts Response Probability of PRRT in Neuroendocrine Tumors.
abstract: OBJECTIVE
  The goal of our study was to quantify the expression of the somatostatin receptors (SSTR2) using the maximum standardized uptake value (SUVmax) of [(68)Ga]DOTA(0)-Phe(1)-Tyr(3)-octreotide (DOTATOC) positron emission tomography (PET)-computed tomography (CT) in liver metastases of patients with neuroendocrine tumors (NETs) prior to peptide receptor radiation therapy (PRRT) and compare the initial tumor uptake with the final treatment outcome.
  
  
  METHODS
  SSTR2 expression of the 60 liver metastases in 30 NET patients was assessed at baseline and after PRRT by measuring SUVmax, tumor to spleen ratio (T/S ratio), and tumor to liver ratio (T/L ratio). Based on morphological changes and tumor size measured at baseline and follow-up contrast-enhanced CT (after three cycles of PRRT), lesions were divided into two groups by the following: (i) responding (n = 40) and (ii) non-responding (n = 20).
  
  
  RESULTS
  Statistically significant differences were observed in the mean SUVmax for non-responding vs. responding lesions at baseline (18.00 ± 3.59 vs. 33.55 ± 4.62, p < 0.05) and for the mean T/S ratio (1.20 ± 0.37 vs. 1.90 ± 0.45, p < 0.05) and the mean T/L ratio (3.15 ± 0.53 vs. 4.97 ± 0.62, p < 0.05). Using the receiver operating characteristic curves, SUVmax was found a better metric than both T/L ratio and T/S ratio (area under the curve (AUC) of SUVmax 0.87; T/L ratio 0.78; T/S ratio 0.73) as a stratification criterion. Using a threshold value of >16.4 for SUVmax, the sensitivity and specificity in predicting responding lesions were 95 and 60 %, respectively.
  
  
  CONCLUSIONS
  We propose a SUVmax cutoff of >16.4 from [(68)Ga]DOTATOC-PET-CT to select patients for PRRT. A T/L ratio >2.2 might present a scanner-independent criterion that enables the translation of our results to other institutions. However, the robustness of this arbitrary unit still needs to be evaluated with different PET scanners.
authors.affiliation: Department of Nuclear Medicine, University Hospital Heidelberg, INF 400, 69120, Heidelberg, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Kratochwil
authors.forename: M
authors.initials: M
authors.lastname: Stefanova
authors.forename: E
authors.initials: E
authors.lastname: Mavriopoulou
authors.forename: T
authors.initials: T
authors.lastname: Holland-Letz
authors.forename: A
authors.initials: A
authors.lastname: Dimitrakopoulou-Strauss
authors.forename: A
authors.initials: A
authors.lastname: Afshar-Oromieh
authors.forename: W
authors.initials: W
authors.lastname: Mier
authors.forename: U
authors.initials: U
authors.lastname: Haberkorn
authors.forename: F L
authors.initials: FL
authors.lastname: Giesel
mesh_terms: D000368:Aged; D003287:Contrast Media; D005260:Female; D006801:Humans; D008113:Liver Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000556:secondary; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D009362:Neoplasm Metastasis; D018358:Neuroendocrine Tumors / Q000000981:diagnostic imaging*; D015282:Octreotide / Q000031:analogs & derivatives / Q000737:chemistry; D009942:Organometallic Compounds / Q000737:chemistry; D010455:Peptides / Q000737:chemistry; D049268:Positron-Emission Tomography; D011336:Probability; D012372:ROC Curve; D019275:Radiopharmaceuticals / Q000737:chemistry; D017481:Receptors, Somatostatin / Q000737:chemistry / Q000378:metabolism*; D014057:Tomography, X-Ray Computed
chemical_list: D003287:Contrast Media; C499142:Ga(III)-DOTATOC; D009942:Organometallic Compounds; D010455:Peptides; D019275:Radiopharmaceuticals; D017481:Receptors, Somatostatin; C574734:SSTR2 protein, human; D015282:Octreotide