ORIGINAL ARTICLE A prospective clinical study of 18 F-FAZA PET-CT hypoxia imaging in head and neck squamous cell carcinoma before and during radiation therapy Stéphanie Servagi-Vernat & Sarah Differding & Francois-Xavier Hanin & Daniel Labar & Anne Bol & John A. Lee & Vincent Grégoire Received: 23 December 2013 /Accepted: 7 February 2014 # Springer-Verlag Berlin Heidelberg 2014 Abstract Purpose Hypoxia in head and neck squamous cell carcinoma (HNSCC) is associated with poor prognosis and out- come. 18 F-Fluoroazomycin arabinoside (FAZA) is a pos- itron emission tomography (PET) tracer developed to enable identification of hypoxic regions within tumor. The aim of this study was to evaluate the use of 18 F-FAZA-PET for assessment of hypoxia before and during radiation therapy. Methods Twelve patients with locally advanced HNSCC underwent 18 F-FAZA-PET scans before and at fraction 7 and 17 of concomitant chemo-radiotherapy. A hypoxic voxel was defined as a voxel expressing a standardized uptake value (SUV) equal or above the SUV mean of the posterior contralat- eral neck muscles plus three standard deviations. The frac- tional hypoxic volume fraction (FHV) and the spatial move of hypoxic volumes during treatment were analyzed. Results A hypoxic volume could be identified in ten patients before treatment. FAZA-PET FHV varied from 0 to 54.3 % and from 0 to 41.4 % in the primary tumor and in the involved node, respectively. Six out of these ten patients completed all the FAZA-PET-computed tomography (CT) during the radio- therapy. In all patients, FHV and SUV max values decreased. All patient presented a spatial move of hypoxic volume, but only three patients had newborn hypoxic voxels after 17 fractions. Conclusion This study indicated that 18 F-FAZA-PET could be used to identify and quantify tumor hypoxia before and during concomitant radio-chemotherapy in patients with lo- cally advanced HNSCC. In addition to the information on prognostic value, the use of 18 F-FAZA-PET allowed the de- lineation of hypoxic volumes for dose escalation protocols. However, due to fluctuation of hypoxia during treatment, repeated scan will have to be performed (i.e. adaptive radiotherapy). Keywords Positronemissiontomography(PET) . 18 F FAZA . Hypoxia imaging . Head and neck squamous cell carcinoma . Radiotherapy Introduction Low oxygen partial pressure (pO 2 ) in solid tumors results from an imbalance between oxygen delivery and oxygen consumption, and has been observed in a wide variety of solid human tumors [1]. In patients with head and neck squamous cell carcinoma (HNSCC), hypoxia has been shown to be an important negative prognostic indicator per se, and a factor of radiation resistance [2–4]. Hence, various therapeutic inter- ventions have been proposed to counteract hypoxia in patients treated with radiotherapy including the use of hypoxic cell sensitizers, carbogen, and heavy ions [5–9]. Interestingly, it has been recently observed that the use of the hypoxic cell radiosensitizer nimorazole was only beneficial in patients expressing a molecular signature of hypoxia, thus S. Servagi-Vernat : S. Differding : D. Labar : A. Bol : J. A. Lee : V. Grégoire Department of Radiation Oncology and Center of Molecular Imaging, Radiotherapy and Oncology (MIRO), Institut de Recherche Clinique (IREC), Université catholique de Louvain, St-Luc University Hospital, Brussels, Belgium F.<X. Hanin Department of Nuclear Medicine and Center of Molecular Imaging, Radiotherapy and Oncology (MIRO), Institut de Recherche Clinique (IREC), Université catholique de Louvain, St-Luc University Hospital, Brussels, Belgium Present Address: S. Servagi-Vernat (*) Department of Radiation Oncology, University Hospital Jean Minjoz, Boulevard Fleming, F-25000 Besancon, France e-mail: stephanie.servagi@gmail.com Eur J Nucl Med Mol Imaging DOI 10.1007/s00259-014-2730-x