Hypoxia imaging with FAZA-PET and theoretical considerations with regard to dose painting for individualization of radiotherapy in patients with head and neck cancer.
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.
Grosu
Anca-Ligia
AL
Department of Radiation Oncology, Klinikum Rechts der Isar, Technical University Munich, Munich, Germany. agrosu@partners.org
Souvatzoglou
Michael
M
Röper
Barbara
B
Dobritz
Martin
M
Wiedenmann
Nicole
N
Jacob
Vesna
V
Wester
Hans-Jürgen
HJ
Reischl
Gerald
G
Machulla
Hans-Juergen
HJ
Schwaiger
Markus
M
Molls
Michael
M
Piert
Morand
M
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
D005462:Fluorine Radioisotopes; D009593:Nitroimidazoles; C498052:fluoroazomycin arabinoside