Phase II Clinical Trial of De-Intensified Therapy in Human Papilloma Virus (HPV) Associated Oropharyngeal Squamous Cell Carcinoma

Inclusion Criteria: * Histologically confirmed or suspected HPV associated squamous cell carcinoma of the oropharynx. * p16 immunohistochemistry is the surrogate marker for HPV positivity and will be scored as positive if there is strong and diffuse nuclear and cytoplasmic staining present in greater than 70% of the tumor specimen. (A negative result excludes the patient from the trial) * In the case of equivocal p16, High Risk HPV (HR HPV), In-Situ Hybridization (ISH) / Polymerase Chain Reaction (PCR) may be performed to determine HPV positivity * AJCC TNM 7th edition stage T1-T3, N0-N2b (or AJCC TNM 8th edition stage T1-T3 N0-N1) disease. * Staging will be based on cross sectional imaging investigations and clinical exam. * Patients who initially have an unknown primary but subsequently have a primary site identified on pathology after surgical resection may be included in the study. * Multidisciplinary team decision to treat with primary transoral resection and neck dissection. * Patients considered fit for surgery and adjuvant therapy. * Aged 18 or over. * Written informed consent provided. Exclusion Criteria: * HPV negative squamous cell carcinomas of the head and neck * T4 and/or T1-T3 tumors where transoral surgery is considered not feasible or there is a high likelihood of positive margins. * AJCC TNM 7th edition N2c-N3 nodal disease (or AJCC TNM 8th edition N2-N3 nodal disease) or high likelihood of gross extranodal extension. * Patients for whom transoral surgery and neck dissection is not considered the primary treatment modality. * Distant metastatic disease as determined by routine pre-operative staging radiological investigations e.g. CT thorax and upper abdomen or PET CT. * Women who are pregnant or breastfeeding * Prior history of radiation to head and neck