title: High-grade glioma radiation therapy target volumes and patterns of failure obtained from magnetic resonance imaging and 18F-FDOPA positron emission tomography delineations from multiple observers.
abstract: OBJECTIVE
  The objective of this study was to compare recurrent tumor locations after radiation therapy with pretreatment delineations of high-grade gliomas from magnetic resonance imaging (MRI) and 3,4-dihydroxy-6-[(18)F]fluoro-L-phenylalanine ((18)F-FDOPA) positron emission tomography (PET) using contours delineated by multiple observers.
  
  
  METHODS
  Nineteen patients with newly diagnosed high-grade gliomas underwent computed tomography (CT), gadolinium contrast-enhanced MRI, and (18)F-FDOPA PET/CT. The image sets (CT, MRI, and PET/CT) were registered, and 5 observers contoured gross tumor volumes (GTVs) using MRI and PET. Consensus contours were obtained by simultaneous truth and performance level estimation (STAPLE). Interobserver variability was quantified by the percentage of volume overlap. Recurrent tumor locations after radiation therapy were contoured by each observer using CT or MRI. Consensus recurrence contours were obtained with STAPLE.
  
  
  RESULTS
  The mean interobserver volume overlap for PET GTVs (42% ± 22%) and MRI GTVs (41% ± 22%) was not significantly different (P=.67). The mean consensus volume was significantly larger for PET GTVs (58.6 ± 52.4 cm(3)) than for MRI GTVs (30.8 ± 26.0 cm(3), P=.003). More than 95% of the consensus recurrence volume was within the 95% isodose surface for 11 of 12 (92%) cases with recurrent tumor imaging. Ten (91%) of these cases extended beyond the PET GTV, and 9 (82%) were contained within a 2-cm margin on the MRI GTV. One recurrence (8%) was located outside the 95% isodose surface.
  
  
  CONCLUSIONS
  High-grade glioma contours obtained with (18)F-FDOPA PET had similar interobserver agreement to volumes obtained with MRI. Although PET-based consensus target volumes were larger than MRI-based volumes, treatment planning using PET-based volumes may not have yielded better treatment outcomes, given that all but 1 recurrence extended beyond the PET GTV and most were contained by a 2-cm margin on the MRI GTV.
authors.affiliation: Department of Medical Physics, British Columbia Cancer Agency, Vancouver, British Columbia, Canada. Electronic address: rkosztyla@bccancer.bc.ca.
authors.forename: Robert
authors.initials: R
authors.lastname: Kosztyla
authors.forename: Elisa K
authors.initials: EK
authors.lastname: Chan
authors.forename: Fred
authors.initials: F
authors.lastname: Hsu
authors.forename: Don
authors.initials: D
authors.lastname: Wilson
authors.forename: Roy
authors.initials: R
authors.lastname: Ma
authors.forename: Arthur
authors.initials: A
authors.lastname: Cheung
authors.forename: Susan
authors.initials: S
authors.lastname: Zhang
authors.forename: Vitali
authors.initials: V
authors.lastname: Moiseenko
authors.forename: Francois
authors.initials: F
authors.lastname: Benard
authors.forename: Alan
authors.initials: A
authors.lastname: Nichol
mesh_terms: D000328:Adult; D000368:Aged; D001254:Astrocytoma / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy; D001932:Brain Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy; D003287:Contrast Media; D004295:Dihydroxyphenylalanine / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D005260:Female; D005462:Fluorine Radioisotopes / Q000493:pharmacokinetics; D005682:Gadolinium; D005909:Glioblastoma / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy; D005910:Glioma / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods; D009364:Neoplasm Recurrence, Local / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy; D015588:Observer Variation; D009837:Oligodendroglioma / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D011880:Radiotherapy Planning, Computer-Assisted; D012680:Sensitivity and Specificity; D047368:Tumor Burden; D055815:Young Adult
chemical_list: D003287:Contrast Media; D005462:Fluorine Radioisotopes; D019275:Radiopharmaceuticals; C043437:fluorodopa F 18; D004295:Dihydroxyphenylalanine; D005682:Gadolinium