The aim of this study is to (i) Determine if tumor hypoxia can be accurately visualised with [18F] HX4 PET imaging in head and neck tumors (ii) correlate the [18F] HX4 PET images with blood and tissue markers and (iii) investigate the quality and optimal timing of [18F] HX4 PET imaging (iv) compare [18F] HX4 PET uptake with [18F] FDG PET uptake before and after treatment.

Tumor hypoxia is the situation where tumor cells are or have been deprived of oxygen. Hypoxic tumor cells are usually more resistant to radiotherapy and chemotherapy and more likely to develop metastasis. In head and neck cancer, tumor hypoxia is known to be an important prognostic factor for long term survival. [18F]HX4 is being developed as a diagnostic radiopharmaceutical for PET imaging to find a marker for hypoxia that can be used in standard clinical practice. Current hypoxia tracers lack reliable image quality and kinetics. Because of the short half life and clearance, we expect that [18F]HX4 will have a higher tumor to background ratio than current nitro-imidazole hypoxia markers such as [18F]-misonidazole. The clinical use of a reliable, non-invasive and easy to use hypoxia imaging agent could allow selection of patients most likely to benefit from hypoxia modifying therapies.

Included are eligible patients with head and neck squamous cell carcinoma (T2, T3, T4, any N, M0) with tumor diameter ≥ 2,5 cm of the oral cavity, oropharynx, hypopharynx or larynx, planned to be treated with curative primary radiation treatment (+/- concurrent chemotherapy). Before treatment a standard planning [18F]FDG PET-CT will be performed, a blood sample is drawn and baseline [18F]HX4 PET scans will be performed. 18F-HX4 scans will be repeated after radiotherapy treatment with 20 +/- 4 Gy (approximately two weeks). Three months after the end of treatment a [18F]FDG PET scan will be performed.

Inclusion Criteria:

• Histological or cytological confirmed HNSSC of the oral cavity, oropharynx, hypopharynx, larynx, T2-T3-T4, any N, M0
• Tumor diameter ≥ 2,5 cm
• WHO performance status 0 to 2
• Scheduled for primary curative (concurrent chemo-) radiotherapy
• No previous surgery to the head and neck
• No previous radiation to the head and neck
• Adequate renal function (calculated creatinine clearance at least 60 ml/min).
• The patient is willing and capable to comply with study procedures
• 18 years or older
• Have given written informed consent before patient registration

Exclusion Criteria:

• No recent (< 3 months) myocardial infarction
• No Uncontrolled infectious disease
• Not pregnant or breast feeding and willing to take adequate contraceptive measures during the study