Treatment adaptation to biological and anatomical changes occurring during treatment can increase the chance of cure at minimized radiation-induced toxicity in head and neck cancer patients. This trial investigates the feasibility of using repetitive per-treatment [18F]FDG-PET acquired during treatment in adaptive [18F]FDG-PET-voxel intensity-based intensity-modulated radiotherapy (IMRT) or volumetric-modulated arc therapy (VMAT) for head and neck cancer.

Inclusion Criteria:

• Histologically confirmed squamous cell carcinoma of the oral cavity, oropharynx, hypopharynx or larynx.
• Primary unresectable tumor and/or patients refused surgery.
• Stage T1-4; T3-4 N0 or Tany N1-3 for cancer of the glottis.
• Multidisciplinary decision of curative radiotherapy or radiochemotherapy.
• Karnofsky performance status ≥70%.
• Age ≥ 18 years old.
• Informed consent obtained, signed and dated before specific protocol procedures.

Exclusion Criteria:

• Treatment combined with brachytherapy.
• Prior irradiation to the head and neck region.
• Distant metastases.
• Second primary tumors that are not under control
• Pregnant or lactating women.
• Creatinine clearance (Cockcroft-Gault) ≤ 60 mL/min before treatment.
• Allergy to the CT-contrast agents.
• Mental condition rendering the patient unable to understand the nature, scope, and possible consequences of the study.
• Patient unlikely to comply with protocol, i.e. uncooperative attitude, inability to return for follow-up visits, and unlikely to complete the study.