Hypofractionated Radiotherapy for Postoperative Intermediate-Risk Head and Neck Squamous Cell Carcinoma

Prior treatment

• Prior radiotherapy or surgery to the head and neck region
• Concurrent other anti-tumor therapy
• Prior neoadjuvant drug therapy
• Evidence of tumor progression on imaging within 28 days before enrollment
• History of severe infection within 1 month before enrollment, including but not limited to infection complications requiring hospitalization, bacteremia, severe pneumonia; any active infection, or unexplained fever \>38.5°C during screening or before first dose

Other illness

• Primary head and neck cancer arising from other sites such as paranasal sinuses, nasopharynx, glottic larynx, skin, or salivary glands
• History of other malignancy within 5 years (except adequately treated in situ cervical cancer or basal cell/squamous cell carcinoma of the skin)
• History of psychoactive substance abuse that cannot be abstained from, or mental disorders

Lab values

• Severe cardiovascular disease: grade II or higher myocardial ischemia or infarction, uncontrolled arrhythmia (including QTc interval ≥450 ms for males or ≥470 ms for females); New York Heart Association (NYHA) class III-IV heart failure, or left ventricular ejection fraction (LVEF) ≤50% on echocardiography

• Age ≥ 18 years
• Eastern Cooperative Oncology Group (ECOG) performance status 0-2
• Histologically or cytologically confirmed stage II-IVA head and neck squamous cell carcinoma (AJCC 8th edition), including oral cavity, oropharynx, hypopharynx, larynx, or cervical lymph node metastasis from unknown primary
• R0 resection and standard neck dissection per surgical evaluation
• Negative surgical margins and no extranodal extension in metastatic lymph nodes on postoperative pathology
• Presence of at least one intermediate-risk factor: close margins (\<5 mm), pT3-4, pN2, lymphovascular invasion, perineural invasion, poor differentiation, or for oral cavity cancer T2 with depth of invasion \>5 mm
• Adequate organ function (without blood transfusion or growth factors within 14 days):
• White blood cell count ≥ 2.0 × 10\^9/L
• Absolute neutrophil count ≥ 1.0 × 10\^9/L
• Platelet count ≥ 80 × 10\^9/L
• Hemoglobin ≥ 90 g/L
• Willing and able to comply with study and follow-up procedures
• Voluntary participation with written informed consent