title: Hypoxia imaging with FAZA-PET and theoretical considerations with regard to dose painting for individualization of radiotherapy in patients with head and neck cancer.
abstract: OBJECTIVE
  To evaluate the role of hypoxia positron emission tomography (PET) using [18F]fluoroazomycin-arabinoside (FAZA) in head and neck cancer for radiation treatment planning using intensity-modulated radiotherapy and dose painting.
  
  
  METHODS
  Eighteen patients with advanced squamous cell head and neck cancer were included. Both FAZA-PET and axial CT were performed using mask fixation. The data were coregistered using software based on mutual information. Contours of tumor (primary gross tumor volume, GTV/CT-P) and lymph node metastases (GTV/CT-N) were outlined manually, and FAZA standardized uptake values (SUVs) were calculated automatically. The hypoxic subvolume (GTV/PET-FAZA) having at least 50% more FAZA uptake than background (mean SUV) neck muscle tissue was contoured automatically within GTV/CT-P (GTV/PET-FAZA-P) and GTV/CT-N (GTV/PET-FAZA-N).
  
  
  RESULTS
  The median GTV/PET-FAZA-P was 4.6 mL, representing 10.8% (range, 0.7-52%) of the GTV/CT-P. The GTV/PET-FAZA-P failed to correlate significantly with the GTV/CT-P (p = 0.06). The median GTV/PET-FAZA-N was 4.1 mL, representing 8.3% (range, 2.2-51.3%) of the GTV/CT-N. It was significantly correlated with the GTV/PET-N (p = 0.006). The GTV/PET-FAZA-P was located in a single confluent area in 11 of 18 patients (61%) and was diffusely dispersed in the whole GTV/CT-P in 4 of 18 patients (22%), whereas no hypoxic areas were identified in 3 of 18 patients (17%). The GTV/PET-FAZA-N was outlined as a single confluent region in 7 of 18 patients (39%), in multiple diffuse hypoxic regions in 4 of 18 patients (22%), and was not delineated in 7 of 18 patients (39%).
  
  
  CONCLUSIONS
  This study demonstrates that FAZA-PET imaging could be used for a hypoxia-directed intensity-modulated radiotherapy approach in head and neck cancer.
authors.affiliation: Department of Radiation Oncology, Klinikum Rechts der Isar, Technical University Munich, Munich, Germany. agrosu@partners.org
authors.forename: Anca-Ligia
authors.initials: AL
authors.lastname: Grosu
authors.forename: Michael
authors.initials: M
authors.lastname: Souvatzoglou
authors.forename: Barbara
authors.initials: B
authors.lastname: Röper
authors.forename: Martin
authors.initials: M
authors.lastname: Dobritz
authors.forename: Nicole
authors.initials: N
authors.lastname: Wiedenmann
authors.forename: Vesna
authors.initials: V
authors.lastname: Jacob
authors.forename: Hans-Jürgen
authors.initials: HJ
authors.lastname: Wester
authors.forename: Gerald
authors.initials: G
authors.lastname: Reischl
authors.forename: Hans-Juergen
authors.initials: HJ
authors.lastname: Machulla
authors.forename: Markus
authors.initials: M
authors.lastname: Schwaiger
authors.forename: Michael
authors.initials: M
authors.lastname: Molls
authors.forename: Morand
authors.initials: M
authors.lastname: Piert
mesh_terms: D000368:Aged; D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000532:radiotherapy; D015687:Cell Hypoxia; D005240:Feasibility Studies; D005260:Female; D005462:Fluorine Radioisotopes; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000532:radiotherapy; D006801:Humans; D008297:Male; D008875:Middle Aged; D009593:Nitroimidazoles; D049268:Positron-Emission Tomography / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods; D014057:Tomography, X-Ray Computed
chemical_list: D005462:Fluorine Radioisotopes; D009593:Nitroimidazoles; C498052:fluoroazomycin arabinoside