This study is an observational study evaluating the clinical outcomes of mucosal sparing proton beam therapy (PBT) after resection of favorable risk oropharyngeal cancer patients. Subjects will be screened at outpatient clinic visit appointments and interested qualified subjects will be consented and offered participation in this study. Once consent has been obtained baseline adverse event and Quality of Life (QOL) data will be collected and subjects will undergo adjuvant PBT and follow-up at 3 months, 12 months, and 24 months. No study-specific visits or evaluations will be required. Patients will be evaluated according to the physician's standard practice and discretion. Patient data will be drawn from the patients' medical records and reported by means of a web-based electronic data collection (EDC) system. Patients will be considered "on study" until 24 months of observation has occurred, withdrawal of consent, lost to follow-up, or study closure.

Inclusion Criteria:

• Resection of oropharyngeal tumor by transoral surgery using frozen section margin analysis resulting in a negative margin resection
• No extensive perineural invasion after review by head and neck pathologist
• No lymphovascular invasion after review by head and neck pathologist
• Pathologic stage T1-2 N1-3 M0 disease

Exclusion Criteria:

• T3 or T4 primary stage disease
• Prior radiation therapy to the head and neck

Oropharyngeal cancer resected using transoral surgery with positive lymphadenopathy requiring adjuvant radiation therapy.