title: Does the pretherapeutic tumor SUV in 68Ga DOTATOC PET predict the absorbed dose of 177Lu octreotate?
abstract: OBJECTIVE
  Selection of candidates for peptide receptor radionuclide therapy (PRRT) is increasingly based on receptor positron emission tomography (PET) imaging, including the common tracer 68Ga DOTATOC. However, no studies have yet compared standardized uptake values (SUVs) and absorbed doses in this field.
  
  
  METHODS
  We retrospectively analyzed a consecutive cohort of 21 patients with 61 evaluable tumor lesions undergoing both pretherapeutic 68Ga DOTATOC-PET/CT (Biograph Duo [Siemens Medical Solutions, Erlangen, Germany]; PET acquisition, 75.3 ± 15.4 minutes postinjection; 117.3 ± 33.9 MBq 68Ga DOTATOC) and PRRT with Lu octreotate (7.47 ± 1.39 GBq; intratherapeutic tumor dosimetry with serial whole-body scans; 1, 2, and 4 days postinjection) at our institution. SUVs were compared with the tumor-absorbed doses per injected activity (D/A0) of the subsequent first treatment cycle.
  
  
  RESULTS
  The correlation of SUV and D/A0 was r = 0.72 (SUVmean) and r = 0.71 (SUVmax), both P < 0.001. Pancreatic origin and hepatic localization were associated with higher D/A0, and chromogranin A level and Ki-67 index had no influence on SUV or D/A0. High-SUV lesions (SUVmean >15; SUVmax >25) resulted in high D/A0 (>10 Gy/GBq) in 66.7% to 70.8% and low D/A0 (<5 Gy/GBq) in only 8.3% to 12.5% on subsequent PRRT. The mentioned low D/A0 range, on the other hand, was achieved by all lesions with SUVmean <7 or SUVmax <9.
  
  
  CONCLUSIONS
  Somatostatin receptor PET imaging may predict tumor-absorbed doses. The ability to indicate insufficient target irradiation by a low SUV could aid in selection of appropriate candidates for PRRT. However, larger series are needed to confirm and validate these initial findings.
authors.affiliation: Department of Nuclear Medicine, University Hospital Bonn, Bonn, Germany. samer.ezziddin@ukb.uni-bonn.de
authors.forename: Samer
authors.initials: S
authors.lastname: Ezziddin
authors.forename: Jonas
authors.initials: J
authors.lastname: Lohmar
authors.forename: Charlotte J
authors.initials: CJ
authors.lastname: Yong-Hing
authors.forename: Amir
authors.initials: A
authors.lastname: Sabet
authors.forename: Hojjat
authors.initials: H
authors.lastname: Ahmadzadehfar
authors.forename: Guido
authors.initials: G
authors.lastname: Kukuk
authors.forename: Hans-Jürgen
authors.initials: HJ
authors.lastname: Biersack
authors.forename: Stefan
authors.initials: S
authors.lastname: Guhlke
authors.forename: Karl
authors.initials: K
authors.lastname: Reichmann
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001692:Biological Transport; D005260:Female; D006801:Humans; D007414:Intestinal Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D008113:Liver Neoplasms / Q000556:secondary; D008297:Male; D008875:Middle Aged; D018358:Neuroendocrine Tumors / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D015282:Octreotide / Q000031:analogs & derivatives* / Q000378:metabolism / Q000627:therapeutic use; D009942:Organometallic Compounds / Q000378:metabolism*; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D049268:Positron-Emission Tomography; D011829:Radiation Dosage; D018000:Receptors, Peptide / Q000378:metabolism; D012189:Retrospective Studies; D013274:Stomach Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D016896:Treatment Outcome
chemical_list: C554548:177Lu-octreotate; C499142:Ga(III)-DOTATOC; D009942:Organometallic Compounds; D018000:Receptors, Peptide; D015282:Octreotide