This is a non-randomized pilot study examining the objective response rate and tolerability of short-course radiotherapy (RT) in elderly patients who are unfit for standard conventional fractionation treatment with head and neck squamous cell carcinoma (HNSCC). There will be two unrelated cohorts in this study: definitive RT and adjuvant RT. Patients will be assigned to the cohorts based on their surgical or non-surgical candidacy. The primary study measure is the locoregional control (LRC) rate of patients at 6 months post RT treated with short-course RT. Locoregional control at one year will be determined by radiographic (PET/CT) and clinical assessment of disease. For the definitive cohort, LRC will be defined as regression in size or disappearance of primary tumor and/or lymph nodes on imaging or clinical examination; and for the adjuvant cohort, LRC will be defined as absence of disease on imaging or no clinical evidence of disease.

To further investigate the treatment regimen, the study team will assess the safety of short-course RT and determine the incidence of serious complications, overall survival (OS), disease-free survival (DFS) within 1 year, and the change in quality of life (QoL) in these patients who are unfit for standard conventional fractionation treatment with head and neck squamous cell carcinoma (HNSCC) as secondary objectives. Secondary endpoints will include 1- year overall survival (OS), 1-year disease-free survival (DFS), and the total score of the Functional Assessment of Cancer Therapy-Head and Neck questionnaire (FACT-H&N). DFS will be defined from the completion of treatment until disease recurrence locally, regionally and/or distantly or until death from disease. OS will be defined from the RT to death or to last follow-up.

As a safety endpoint, the study team will calculate number and proportion of patients developing reportable AEs and SAEs according to relatedness to the treatment and stratified by severity.