A Prospective Single-Arm Study（NCLDR）

【Inclusion Criteria】:

1. Age: 18 to 70 years old (inclusive) at the time of enrollment, based on the Gregorian calendar birth date. Age calculation is based on the date of signing the informed consent form. Includes both males and females.
2. ECOG Performance Status: 0-1.
3. Life Expectancy: ≥ 6 months.
4. Diagnosis: Histologically confirmed oral squamous cell carcinoma.
5. Clinical Stage: Stage III, IVA, or IVB according to AJCC clinical staging.
6. Absence of Distant Metastasis: No evidence of distant metastasis confirmed by auxiliary examinations.
7. Prior Anti-tumor Therapy: No previous surgery, radiotherapy, chemotherapy, immunotherapy, targeted therapy, or other anti-tumor treatments.
8. Measurable Lesion: At least one measurable target lesion according to RECIST 1.1 criteria, confirmed by imaging during the screening period.
9. Adequate Organ Function: Meeting the following criteria:

   * Hematology: White blood cell count (WBC) ≥ 4.0 x 10⁹/L; Absolute neutrophil count (ANC) ≥ 1.5 x 10⁹/L; Hemoglobin (Hb) ≥ 90 g/L; Platelets (PLT) ≥ 100 x 10⁹/L.
   * Liver Function: ALT and AST \< 3 x Upper Limit of Normal (ULN); Total bilirubin \< 1.5 x ULN; Child-Pugh class A or B; Normal liver tissue volume ≥ 700 cm³.
   * Renal Function: Serum creatinine \< 1.5 x ULN.
   * Coagulation: International Normalized Ratio (INR) and Activated Partial ·Thromboplastin Time (APTT) ≤ 1.5 x ULN.
   * Serum Albumin: ≥ 28 g/L.
   * Urinalysis: Urine protein \< 2+ (If baseline urine protein ≥ 2+, a 24-hour urine protein quantification must be performed within 7 days; enrollment requires quantification \< 1g).
   * Electrocardiogram (ECG): No significant abnormalities.
   * Cardiac Function: Left Ventricular Ejection Fraction (LVEF) ≥ 50%.
10. Contraception: Women of childbearing potential must have reliable contraception or have a negative pregnancy test (serum or urine) within 7 days prior to enrollment. They must be willing to use adequate contraception during the trial and for 8 weeks after the last dose of the study drug. Men must agree to use adequate contraception or be surgically sterilized during the trial and for 8 weeks after the last dose of the study drug.
11. Informed Consent: Ability to understand and voluntarily sign the informed consent form (signed by a legal representative if the participant loses capacity), with expected good compliance.

【Exclusion Criteria】:

1. Unsuitable for Treatment: Unsuitable for receiving the protocol-specified low-dose radiotherapy, immunotherapy, and chemotherapy.
2. Prior Anti-tumor Therapy: Previous treatment with anti-tumor therapy, including investigational drugs, chemotherapy, radiotherapy, or prior treatment with anti-PD-1, anti-PD-L1, anti-PD-L2 antibodies/drugs, or any other antibody/drug specifically targeting T-cell co-stimulatory checkpoint pathways.
3. Active Infection: Severe active infection requiring systemic therapy.
4. Cardiovascular/Cerebrovascular Events: History within 6 months prior to study treatment of: myocardial infarction, severe/unstable angina, coronary/peripheral artery bypass graft, symptomatic congestive heart failure, cerebrovascular accident, transient ischemic attack, or symptomatic pulmonary embolism.
5. Bleeding Tendency/Disorder: Definite bleeding tendency or clinically significant bleeding symptoms within 28 days, including but not limited to gastrointestinal bleeding, epistaxis (excluding minor nosebleeds and blood-tinged sputum), or ongoing hemorrhagic or coagulopathic disease.
6. Systemic Corticosteroids: Requirement for systemic corticosteroid therapy (\>10 mg/day prednisone or equivalent dose) or replacement therapy (\>10 mg/day prednisone equivalent) within 14 days prior to study treatment.
7. Recent Procedures: Live vaccination within 4 weeks prior to study treatment or planned during the study period. Major surgery within 4 weeks prior to study treatment.
8. Pregnancy/Lactation: Pregnant or breastfeeding women.
9. Infectious Disease:

   * Known immunodeficiency.
   * Known history of Human Immunodeficiency Virus (HIV) or Acquired --·Immunodeficiency Syndrome (AIDS)-defining illness.
   * Hepatitis B Virus (HBV) infection (HBsAg positive) or Hepatitis C Virus (HCV) ·infection (HCV RNA positive if anti-HCV antibody screening is positive).
   * Known active history of Tuberculosis (TB).
10. Other Exclusionary Conditions: Any other factor identified by the investigator that may lead to premature termination of the study, such as severe laboratory abnormalities, or concomitant familial or social factors that could compromise participant safety or affect data/sample collection.