RecruitingProcedurePersonalized Ultrafractionated Stereotactic Adaptive Radiotherapy for Palliative Head and Neck Cancer Treatment (PULS-Pal)This trial tests how well personalized ultra fractionated stereotactic adaptive radiotherapy (PULSAR) works together with HyperArc© radiation treatment planning technology for palliative (holistic pain and symptom control) tumor control in patients with primary or recurrent, localized or metastatic head and neck cancer (HNC) who are ineligible for or decline standard of care treatment. Researchers want to evaluate if using HyperArc and PULSAR together will deliver higher, possibly more effective doses, resulting in better tumor control with the same or fewer side effects than smaller routine doses. PULSAR is a radiation therapy regimen that uses a limited number of fairly large dose pulses while adjusting to specific anatomic and/or biological changes which may occur during the course of the treatment. HyperArc radiation treatment planning technology is a tool that allows for target dose escalation to tumor tissue while maintaining minimal head and neck organs-at-risk doses compared to other radiation treatment planning software. Undergoing PULSAR and HyperArc technology together may be a safe and effective palliative treatment option for patients with HNC.