title: Exploratory geographical analysis of hypoxic subvolumes using 18F-MISO-PET imaging in patients with head and neck cancer in the course of primary chemoradiotherapy.
abstract: OBJECTIVE
  Hypoxia in head and neck tumours is associated with poor prognosis and outcome, and can be visualized using (18)F-MISO-PET imaging; however, it is not clear whether the size and location of hypoxic subvolumes remain stable during therapy. In a pilot project, we conducted an exploratory analysis of persistent tumour hypoxia during treatment.
  
  
  METHODS
  Sixteen patients with locally advanced head and neck tumours underwent consecutive (18)F-MISO-PET scans before and during primary chemoradiotherapy. The size, location and overlap of the hypoxic subvolumes were analysed using a semi-automatic algorithm based on a tumour to normal tissue ratio of 1.5.
  
  
  RESULTS
  Quantitative evaluation showed tumour hypoxia in week 0 in 16 out of 16 and in week 2 in 5 out of 14 patients. For the five patients with persistent hypoxia, both increased and decreased hypoxic subvolumes could be observed. Mean hypoxic subvolume overlap was 55% of the hypoxic volume of the first scan and 72% of the hypoxic volume of the second scan. A stationary (in four out of five patients) and dynamic component (in three out of five patients) could be differentiated.
  
  
  CONCLUSIONS
  In patients with persistent hypoxia after 2 weeks of treatment, the hypoxic subvolumes showed mostly a geographically relatively stable conformation.
authors.affiliation: Department of Radiation Oncology, University Medical Center Freiburg, Germany. Electronic address: martin-immanuel.bittner@uniklinik-freiburg.de.
authors.forename: Martin-Immanuel
authors.initials: MI
authors.lastname: Bittner
authors.forename: Nicole
authors.initials: N
authors.lastname: Wiedenmann
authors.forename: Sabine
authors.initials: S
authors.lastname: Bucher
authors.forename: Michael
authors.initials: M
authors.lastname: Hentschel
authors.forename: Michael
authors.initials: M
authors.lastname: Mix
authors.forename: Wolfgang A
authors.initials: WA
authors.lastname: Weber
authors.forename: Anca-Ligia
authors.initials: AL
authors.lastname: Grosu
mesh_terms: D015687:Cell Hypoxia; D059248:Chemoradiotherapy; D005260:Female; D005462:Fluorine Radioisotopes; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000628:therapy*; D006801:Humans; D008297:Male; D008920:Misonidazole / Q000031:analogs & derivatives*; D010865:Pilot Projects; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals
chemical_list: D005462:Fluorine Radioisotopes; D019275:Radiopharmaceuticals; C031843:fluoromisonidazole; D008920:Misonidazole
keywords: Biological imaging; Head and neck tumours; Hypoxia imaging; PET; Tumour hypoxia