Inclusion Criteria:

- Non-operated histologically confirmed squamous cell carcinoma of the oral cavity,
oropharynx (except the posterior wall) and lymph node metastases from the unknown
primary tumor (CUP)

- Stage T1-4; Tx N+ for the CUP

- Multidisciplinary Group of Head and Neck Tumors at Ghent University Hospital decision
of radical radiotherapy (±concurrent chemotherapy)

- Informed consent obtained, signed and dated before specific protocol procedures.

Exclusion Criteria:

- Age < 18 years

- Pregnant or lactating women

- Active infection or fistula in the oral/oropharyngeal mucosa

- Previous cancer of the oral cavity and the oropharynx

- Prior head-and-neck radiotherapy

- Expectation of non-compliance with the study protocol

- Known allergy for topical anesthetics (Xylocaïne)