A Feasibility Study on Adaptive 18F-FDG-guided Radiotherapy for Recurrent and Second Primary Head and Neck Cancer in the Previously Irradiated Territory.

Inclusion Criteria:

* Histologically confirmed recurrences and second primary squamous cell carcinoma of the oral cavity, oropharynx, hypopharynx or larynx in the previously irradiated territory.
* Primary unresectable tumor and/or patients refused surgery.
* No grade 3 or more late toxicity (except xerostomia) after the initial radio(chemo)therapy for primary head and neck cancer.
* Minimal interval 12 months after the initial radio(chemo)therapy for primary head and neck cancer.
* Decision of a multidisciplinary tumor board on curative radiotherapy (in combination or not with targeted therapy with cetuximab)
* Karnofsky performance status ≥70%.
* Age ≥ 18 years old.
* Informed consent obtained, signed and dated before specific protocol procedures.

Exclusion Criteria:

* Previous radiotherapy for cT1-2 cN0 M0 glottic cancer.
* Brachytherapy as treatment for second primary / recurrence.
* Distant metastases.
* Other second primary tumors that are not under control.
* Pregnant or lactating women.
* Elevated blood creatinine level.
* 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.