A Single Arm Phase II Trial in p16-positive Oropharynx Cancer of Selective Dose De-escalation of nodAl VolumEs at Minimal Risk and Primary Site Disease (SAVED)

Patients with human papillomavirus (HPV)-related oropharyngeal cancer generally have very good outcomes. Patients' treatment responses depend more on their individual cancer characteristics and personal risk factors than on the specific type of treatment they receive. However, the different treatments used for this cancer can cause significant side effects. Because outcomes are often favorable regardless of treatment type, reducing treatment-related side effects should be a priority when choosing care. Studies have reported that lowering radiation doses for some patients can reduce side effects while still effectively controlling the cancer. Patients with this type of head and neck cancer typically receive either surgery or radiation as their first treatment. For patients who receive surgery first, radiation to the surgical area and nearby neck lymph nodes is often recommended afterward. In these patients, the study will test whether lowering the radiation dose to low-risk lymph nodes on the side of the neck opposite the tumor can reduce side effects while still effectively controlling the cancer (Method A). For patients who receive radiation as their first treatment, the study will test one or both of two radiation approaches aimed at reducing both short-term and long-term side effects. These approaches include reduced lymph node radiation (Method A, described above) and a tumor dose reduction approach (Method B), which lowers the radiation dose delivered directly to the tumor. Information such as tumor size, the number of cancerous or suspicious lymph nodes, and risk factors like smoking history will be used to determine which patients may be eligible for reduced lymph node radiation (Method A), reduced tumor radiation (Method B), or both. Patients who may qualify for tumor dose reduction (Method B), either alone or combined with Method A, will need an additional blood test called a circulating tumor DNA (ctDNA) test to determine eligibility. The ctDNA test measures small amounts of tumor-related DNA in the blood, which are often elevated at the time of diagnosis. Studies have shown that cancer is more likely to return when ctDNA levels remain positive after treatment. This study will evaluate whether ctDNA levels measured before and during treatment can help identify patients who can safely receive lower radiation doses to the tumor (Method B). Overall, this study aims to safely evaluate two radiation de-escalation approaches in order to lessen short- and long-term side effects while maintaining excellent cancer control.