Impact of Postoperative Radiotherapy Versus PD-1 Inhibitor Maintenance on Survival in Resectable Locally Advanced Oral and Oropharyngeal Squamous Cell Carcinoma

Inclusion Criteria: 1. Age 18-80 years, any gender. 2. Expected survival ≥ 6 months. 3. Adequate major organ function; ECOG performance status 0-1. 4. Treatment-naïve patients diagnosed with locally advanced oral squamous cell carcinoma (LA-OSCC) or locally advanced oropharyngeal squamous cell carcinoma (LA-OPSCC), in accordance with the 8th edition of the American Joint Committee on Cancer (AJCC) staging system (2017) and the 2020 Chinese Stomatological Association (CSA) guidelines for pathological diagnosis of oral and oropharyngeal cancers, with clinical stages: cT3N0M0, cT1-3N1M0, cT4aN0-2M0, cT1-4aN3M0, or cT4bN0-3M0. 5. No evidence of distant metastasis based on auxiliary examinations. 6. No prior antitumor treatment, including surgery, radiotherapy, chemotherapy, immunotherapy, targeted therapy, or other antitumor therapies. 7. Received 2 cycles of neoadjuvant chemoimmunotherapy (toripalimab + TP regimen) and underwent R0 resection. 8. Women of childbearing potential must agree to use effective contraception during treatment and for 3 months after. 9. Signed informed consent (if the participant lacks capacity, by a legally authorized representative), voluntarily participates in the study, and demonstrates good compliance. Exclusion Criteria: 1. History of radiotherapy to the head and neck region. 2. Severe bone marrow suppression, hepatic or renal failure, or uncontrolled severe infections, cardiovascular diseases, or other conditions that may preclude tolerance of treatment. 3. Active autoimmune diseases, history of organ transplantation requiring long-term immunosuppressive therapy, or severe immunodeficiency that may result in serious immune-related adverse events. 4. Active infections requiring systemic therapy. 5. Cardiovascular/cerebrovascular events within 6 months prior to study treatment, including myocardial infarction, severe/unstable angina, coronary or peripheral artery bypass surgery, symptomatic heart failure, cerebrovascular accident, transient ischemic attack, or symptomatic pulmonary embolism. 6. Bleeding tendency/disorders: clinically significant bleeding or clear bleeding tendency within the past 28 days, including but not limited to gastrointestinal bleeding, epistaxis (excluding mild nosebleeds or blood-streaked sputum), or persistent bleeding/clotting disorders. 7. History of substance abuse, alcoholism, or drug abuse. 8. Pregnant or breastfeeding women. 9. Participation in other interventional clinical trials simultaneously.