title: 18F-FDG PET during stereotactic body radiotherapy for stage I lung tumours cannot predict outcome: a pilot study.
abstract: OBJECTIVE
  (18)F-Fluorodeoxyglucose positron emission tomography (FDG PET) has been used to assess metabolic response several months after stereotactic body radiotherapy (SBRT) for early-stage non-small cell lung cancer. However, whether a metabolic response can be observed already during treatment and thus can be used to predict treatment outcome is undetermined.
  
  
  METHODS
  Ten medically inoperable patients with FDG PET-positive lung tumours were included. SBRT consisted of three fractions of 20 Gy delivered at the 80% isodose at days 1, 6 and 11. FDG PET was performed before, on day 6 immediately prior to administration of the second fraction of SBRT and 12 weeks after completion of SBRT. Tumour metabolism was assessed semi-quantitatively using the maximum standardized uptake value (SUV(max)) and SUV(70%).
  
  
  RESULTS
  After the first fraction, median SUV(max) increased from 6.7 to 8.1 (p = 0.07) and median SUV(70%) increased from 5.7 to 7.1 (p = 0.05). At 12 weeks, both median SUV(max) and median SUV(70%) decreased by 63% to 3.1 (p = 0.008) and to 2.5 (p = 0.008), respectively.
  
  
  CONCLUSIONS
  SUV increased during treatment, possibly due to radiation-induced inflammation. Therefore, it is unlikely that (18)F-FDG PET during SBRT will predict treatment success.
authors.affiliation: Department of Radiation Oncology, University Medical Center Groningen, University of Groningen, PO Box 30.001, 9700 RB Groningen, The Netherlands. E.M.Wiegman@rt.umcg.nl
authors.forename: Erwin M
authors.initials: EM
authors.lastname: Wiegman
authors.forename: Jan
authors.initials: J
authors.lastname: Pruim
authors.forename: Jan F
authors.initials: JF
authors.lastname: Ubbels
authors.forename: Harry J M
authors.initials: HJ
authors.lastname: Groen
authors.forename: Johannes A
authors.initials: JA
authors.lastname: Langendijk
authors.forename: Joachim
authors.initials: J
authors.lastname: Widder
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery* / Q000628:therapy; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D010865:Pilot Projects; D049268:Positron-Emission Tomography; D016634:Radiosurgery; D016896:Treatment Outcome
chemical_list: D019788:Fluorodeoxyglucose F18