The purpose of this study is to see how useful the information provided from Positron Emission Tomography (PET) scans can be in the actual planning and delivery of radiation treatment to patients who have head and neck cancers. Patients participating in this study, will have (in addition to their routine tests) a PET scan before and during their radiation treatment. Following the intervention, patients will be followed as per standard practice.

Inclusion Criteria:

• Non-nasopharynx head and neck mucosal squamous cell carcinoma
• Radiologically evident gross disease
• Radiotherapy alone for curative intent
• Age equal to or more than 18 years old
• To be eligible for the second study PET-CT scan: FDG avid tumour (or minimum SUV of 2.5) on the first study PET-CT scan

Exclusion Criteria:

• Nasopharynx cancer
• H&N SCC skin
• Distant metastases (already known or if found on baseline CT-thorax)
• Prior malignancy within the last 5 years (exclude non-H&N SCC, BCC skin)
• Prior chemotherapy within the last 5 years or concurrent chemotherapy/EGFR inhibitors
• Prior head and neck radiotherapy
• Inability to lie supine for study duration
• Pregnancy
• Inability to provide informed consent