Adaptive De-intensified Radiotherapy Using Circulating Tumor DNA in HPV- Associated Oropharyngeal Cancer

Inclusion Criteria: * Pathologically confirmed diagnosis of squamous cell carcinoma of the oropharynx (unknown primary, base of tongue, tonsil, oropharyngeal walls, soft palate). Cytologic or fine needle aspiration (FNA) confirmation is sufficient if a biopsy of the primary tumor is not feasible * P16 positive immunohistochemical staining. FNA may be used as the sole diagnostic tissue. If staining was done at an outside hospital, central review by the Ohio State University (OSU) department of pathology must occur prior to trial enrollment * Clinical stage T0, N1-N2, T1-2, N1-N2, T3-T4, N0-2 (American Joint Committee on Cancer \[AJCC\] 8th edition) including no evidence of distant metastases based on general history, imaging, physical examination, and examination with laryngopharyngoscopy * Clinical or radiographic evidence of measurable disease at the primary site or lymph nodes. Simple tonsillectomy or excision of primary without removal of nodal disease is permitted, as is excision of gross nodes but with intact primary site * Fludeoxyglucose F-18 (FDG) PET/CT from the base of skull to the mid-thigh is mandatory and patients cannot be enrolled without a pretreatment PET/CT. PET/CT must be completed prior to enrollment * Pretreatment tumor tissue modified HPV virus (TTMV-HPV) particles present in plasma cell free DNA value of \>= 200 copies/mL at baseline * Patients must provide their smoking history prior to enrollment. Patients must have =\< 10 pack years of smoking. The …