title: Positron emission tomography/computed tomography imaging of residual skull base chordoma before radiotherapy using fluoromisonidazole and fluorodeoxyglucose: potential consequences for dose painting.
abstract: OBJECTIVE
  To detect the presence of hypoxic tissue, which is known to increase the radioresistant phenotype, by its uptake of fluoromisonidazole (18F) (FMISO) using hybrid positron emission tomography/computed tomography (PET/CT) imaging, and to compare it with the glucose-avid tumor tissue imaged with fluorodeoxyglucose (18F) (FDG), in residual postsurgical skull base chordoma scheduled for radiotherapy.
  
  
  METHODS
  Seven patients with incompletely resected skull base chordomas were planned for high-dose radiotherapy (dose ≥70 Gy). All 7 patients underwent FDG and FMISO PET/CT. Images were analyzed qualitatively by visual examination and semiquantitatively by computing the ratio of the maximal standardized uptake value (SUVmax) of the tumor and cerebellum (T/C R), with delineation of lesions on conventional imaging.
  
  
  RESULTS
  Of the eight lesion sites imaged with FDG PET/CT, only one was visible, whereas seven of nine lesions were visible on FMISO PET/CT. The median SUVmax in the tumor area was 2.8 g/mL (minimum 2.1; maximum 3.5) for FDG and 0.83 g/mL (minimum 0.3; maximum 1.2) for FMISO. The T/C R values ranged between 0.30 and 0.63 for FDG (median, 0.41) and between 0.75 and 2.20 for FMISO (median,1.59). FMISO T/C R >1 in six lesions suggested the presence of hypoxic tissue. There was no correlation between FMISO and FDG uptake in individual chordomas (r = 0.18, p = 0.7).
  
  
  CONCLUSIONS
  FMISO PET/CT enables imaging of the hypoxic component in residual chordomas. In the future, it could help to better define boosted volumes for irradiation and to overcome the radioresistance of these lesions. No relationship was founded between hypoxia and glucose metabolism in these tumors after initial surgery.
authors.affiliation: Radiation Oncology Department, Antoine Lacassagne Center, Nice, France. hamid.mammar@unice.fr
authors.forename: Hamid
authors.initials: H
authors.lastname: Mammar
authors.forename: Khaldoun
authors.initials: K
authors.lastname: Kerrou
authors.forename: Valérie
authors.initials: V
authors.lastname: Nataf
authors.forename: Dominique
authors.initials: D
authors.lastname: Pontvert
authors.forename: Stéphane
authors.initials: S
authors.lastname: Clemenceau
authors.forename: Guillaume
authors.initials: G
authors.lastname: Lot
authors.forename: Bernard
authors.initials: B
authors.lastname: George
authors.forename: Marc
authors.initials: M
authors.lastname: Polivka
authors.forename: Karima
authors.initials: K
authors.lastname: Mokhtari
authors.forename: Regis
authors.initials: R
authors.lastname: Ferrand
authors.forename: Loïc
authors.initials: L
authors.lastname: Feuvret
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Habrand
authors.forename: Jacques
authors.initials: J
authors.lastname: Pouysségur
authors.forename: Nathalie
authors.initials: N
authors.lastname: Mazure
authors.forename: Jean-Noël
authors.initials: JN
authors.lastname: Talbot
mesh_terms: D000328:Adult; D015687:Cell Hypoxia; D002817:Chordoma / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000532:radiotherapy; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics; D006801:Humans; D008297:Male; D008875:Middle Aged; D008920:Misonidazole / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D064847:Multimodal Imaging / Q000379:methods*; D009364:Neoplasm Recurrence, Local; D049268:Positron-Emission Tomography; D011446:Prospective Studies; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D019292:Skull Base Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000532:radiotherapy; D014057:Tomography, X-Ray Computed; D055815:Young Adult
chemical_list: D019275:Radiopharmaceuticals; C031843:fluoromisonidazole; D019788:Fluorodeoxyglucose F18; D008920:Misonidazole