This is a single-arm, observational registry study determining the effects of reduced radiation dose in select patients with human papillomavirus (HPV) positive oropharyngeal cancer.

Inclusion Criteria:

• Pathologically (histologically or cytologically) proven (from primary lesion and/or lymph nodes) diagnosis of human papillomavirus (HPV)-positive oropharyngeal squamous cell carcinoma. HPV-positivity will be defined as tumors that are p16-positive by immunohistochemistry. Numerous studies have demonstrated near 100% agreement between p16 and HPV for patients with oropharyngeal cancer. As such, the use of p16 has been accepted as an appropriate surrogate for HPV status.
• Clinical stage I, II, or III disease (AJCC Eighth Edition); Note: Patients with M1 tumors (distant metastases) are not eligible;
• History/physical examination within 6 weeks prior to registration, including assessment of weight and recent weight loss;
• Age ≥ 18;
• PET/CT within 6 weeks prior to registration;
• Patients must sign a study-specific informed consent form prior to study entry.
• Both men and women and members of all races and ethnic groups are eligible for this trial. Non-English speaking, deaf, hard of hearing and illiterate individuals are eligible for this trial.

Exclusion Criteria:

• Prior invasive malignancy (except non-melanomatous skin cancer) unless disease free for a minimum of 3 years;
• Patients who have had initial surgical treatment other than the diagnostic biopsy of the primary site or nodal sampling of the neck disease are excluded;
• Prior systemic chemotherapy for the study cancer; note that prior chemotherapy for a different cancer is allowable;
• Receipt of prior radiotherapy that would result in overlap with proposed field.

Patients with HPV-positive oropharyngeal cancer