Inclusion Criteria:
1. Subjects with pathologically confirmed primary head and neck squamous cell carcinoma (excluding nasopharyngeal cancer);
2. Aged 18-75 years, of any gender
3. Subjects in clinical stage III-IVb (TNM staging, 8th edition); for oropharyngeal squamous cell carcinoma (P16-), the stage shall be III-IVb; for oropharyngeal squamous cell carcinoma (P16+), the stage shall be III.
4. Subjects with no prior anti-tumor therapy such as radiotherapy, chemotherapy, immunotherapy, or biotherapy for the current head and neck tumors;
5. Eastern Cooperative Oncology Group (ECOG) performance status score of 0-1;
6. Estimated survival time ≥ 6 months;
7. Subjects with no obvious contraindications to immunotherapy, chemoradiotherapy and surgery;
8. Subjects who are willing to undergo surgical treatment;
9. Subjects with major organ function levels meeting the following criteria:
1. Hematology must meet the following criteria: White blood cell (WBC) count ≥4.0×10\^9/L, absolute neutrophil count (ANC) ≥1.5×10\^9/L, platelet (PLT) count ≥100×10\^9/L, hemoglobin (Hb) ≥90 g/L (no blood transfusion or blood products within 14 days, and no correction with granulocyte-colony stimulating factor (G-CSF) or other hematopoietic stimulating factors);
2. Blood chemistry must meet the following criteria: Serum albumin ≥ 3.0 g/dL (30 g/L), total bilirubin (TBIL) ≤1.5×upper limit of normal (ULN), alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤2.5×ULN, blood urea nitrogen (BUN) and creatinine (CRE) ≤1.5×ULN or endogenous creatinine clearance ≥60 mL/min (Cockcroft-Gault formula);
3. Good coagulation function: Defined as an international normalized ratio (INR) or prothrombin time (PT) ≤1.5 times ULN; if the subject is receiving anticoagulant therapy, the PT must be within the intended therapeutic range for the anticoagulant drug;
10. Women of childbearing potential must have a negative pregnancy test (serum or urine) within 7 days before enrollment and be willing to use effective methods of contraception during the study and for 6 months after the last dose of the anti-PD-1 antibody. For male subjects whose partners are women of childbearing potential, effective methods of contraception must be used during the study and for 6 months after the last dose of the anti-PD-1 antibody;
11. Subjects who voluntarily participate in this study, sign the informed consent form (ICF), have good compliance, and cooperate with follow-up.
Exclusion Criteria:
1. Subjects who have received prior treatment with anti-PD-1/programmed death-ligand 1 (PD-L1) antibodies, anti-programmed death-ligand 2 (PD-L2) antibodies, anti-cluster of differentiation 137 (CD137) antibodies, anti-cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) antibodies, or other drugs/antibodies targeting T-cell co-stimulation or checkpoint pathways;
2. Subjects with a severe, active autoimmune disease. Subjects in a stable condition who do not require systemic immunosuppression are allowed to be enrolled, such as those with: Type I diabetes mellitus, hypothyroidism requiring only hormone replacement therapy, and skin diseases not requiring systemic treatment (e.g., vitiligo, psoriasis, and alopecia);
3. Subjects with congenital or acquired immunodeficiency (e.g., human immunodeficiency virus (HIV) infection), active hepatitis B (hepatitis B virus (HBV)-DNA ≥10\^4 copies/mL), or active hepatitis C (hepatitis C antibody positive, and HCR-RNA above the lower limit of detection of the analytical method);
4. Subjects with known allergy to the study drug or any of its excipients; or a history of severe allergic reactions to other monoclonal antibodies.
5. Subjects with the following conditions within 6 months prior to randomization: myocardial infarction, severe/unstable angina pectoris, cardiac insufficiency of NYHA Class II or higher, clinically significant supraventricular or ventricular arrhythmia, and symptomatic congestive heart failure.
6. Subjects who have received a live vaccine within 4 weeks before the first dose of the study drug. Inactivated virus vaccines for seasonal influenza administered by injection are permitted, but live attenuated influenza vaccines administered nasally are not permitted;
7. Subjects with known history of allogeneic organ transplant or allogeneic stem cell transplant.
8. Subjects with known history of psychoactive drug abuse or drug addiction.
9. Pregnant or lactating women;
10. Subjects with diagnosis of any other malignant tumors within 5 years prior to study entry, with the exception of cutaneous basal cell carcinoma or squamous cell carcinoma, superficial bladder cancer, cervical carcinoma in situ, ductal carcinoma in situ of the breast, and papillary thyroid cancer that have been locally treated and cured;
11. Subjects with other serious physical or mental illnesses or laboratory test abnormal findings that may increase the risk of study participation, or interfere with study results, and patients whom the investigator deems unsuitable for participation in this study.
