Trial of Magnetic Resonance Imaging Guided Radiotherapy Dose Adaptation in Human Papilloma Virus Positive Oropharyngeal Cancer

Inclusion Criteria: * Biopsy proven diagnosis of squamous cell carcinoma of the oropharynx (tonsil, base of tongue, soft palate, or oropharyngeal walls). Clinical evidence should be documented, and may consist of imaging, endoscopic evaluation, palpation, and should be sufficient to estimate the size of the primary for purposes of T staging. * Age ≥18 years * Clinical stage T1-3, N0-2 (AJCC, 8th ed.), with no distant metastases, based on routine staging workup. * Positive for HPV by p16 IHC or ISH * Lifetime pack-year history of \<10 years, currently non-smoking for at least 5 years. * No head and neck surgery of the primary tumor or lymph nodes except for incisional or excisional biopsies. * No retropharyngeal nor level IV (or lower) lymphadenopathy (i.e. nodes in level I-III only) * Eastern Cooperative Oncology Group (ECOG) = 0, 1, or 2. * Dispositioned to photon/proton radiotherapy +/- chemotherapy * For females of child-bearing age, a negative pregnancy test Exclusion Criteria: * Patients who have undergone definitive resection of their primary or nodal disease as well as any chemotherapy or radiation therapy for their HNSCC. * Pregnant or breast-feeding females * Clinically significant uncontrolled major cardiac, respiratory, renal, hepatic, gastrointestinal or hematologic disease but not limited to: * Symptomatic congestive heart failure, unstable angina, or cardiac dysrhythmia not controlled by pacer device * Myocardial infarction within 3 months of registration * C…