A Phase II Study for p16+ Oropharyngeal Cancer PerSonalized De-escalation Treatment at University of MIchigan (CuSToMIze)

Cohort A will undergo initial surgical resection of the primary and neck dissection with pathologic features directing predetermined adjuvant treatment. Pathology of the primary and nodal specimens will then be reviewed as to determine the next intervention per protocol. Based on operative findings including degree of nodal involvement, extracapsular spread, perineural invasion, and lymphovascular involvement, patients will be designated to adjuvant treatment arms consisting of observation, adjuvant radiation, or adjuvant chemoradiation.

Patients will receive an initial plan with a single prescription of 30 Gy in 15 fractions to PTV\_High and PTV\_Low with RT given once daily, 5 days a week (Monday through Friday). After analysis of mid-treatment PET/CT, the remaining radiation treatment will be delivered as a conedown to the gross disease only. Patients will be planned to receive a total dose of 70 Gy, 54 Gy, or 44 Gy to PTV\_High in 2 Gy per fraction.

Cohort A will undergo initial surgical resection of the primary and neck dissection with pathologic features directing predetermined adjuvant treatment. Pathology of the primary and nodal specimens will then be reviewed as to determine the next intervention per protocol. Based on operative findings including degree of nodal involvement, extracapsular spread, perineural invasion, and lymphovascular involvement, patients will be designated to adjuvant treatment arms consisting of observation, adjuvant radiation, or adjuvant chemoradiation.

Patients will receive adjuvant radiation based on pathologic features.Total radiation treatment doses and prescriptions will include 36 Gy in 18 fractions, 50 Gy in 25 fractions and 60 Gy in 30 fractions.