Inclusion Criteria:  Age ≥18 years Ability to provide written informed consent. Stage T3-T4N0-3 as per AJCC 8th edition Eastern Cooperative Oncology Group (ECOG) performance status 0-2. Biopsy proven diagnosis of squamous cell carcinoma of the oropharynx. Planned for curative radiotherapy +/- chemotherapy For females of child-bearing age, a negative pregnancy test Patients treated with induction chemotherapy can be included if they have residual tumor in place.  Exclusion Criteria:  Previous irradiation of the head and neck (HNC) region, excluding superficial radiation therapy for non-melanomatous skin cancer Previous surgery of the HNC region (except for incisional or excisional biopsies) Pregnancy or breastfeeding Connective tissue disease Any medical condition that could, in the opinion of the investigator, prevent follow-up after radiotherapy. Patients with contra-indications to MRI will be excluded.