Postoperative Radiotherapy With Nimotuzumab ± Benmelstobart in Intermediate-Risk Head and Neck Squamous Cell Carcinoma

Inclusion Criteria: * Age ≥ 18 years * ECOG performance status: 0-2 * Histologically confirmed squamous cell carcinoma of the head and neck (oral cavity, oropharynx, larynx); oropharyngeal cancer must be p16-negative (p16 positivity defined as ≥70% staining) * Completionof curative-intent surgery, with any of the following intermediate-risk factors present postoperatively: ①pT3-4a; ②N2 disease (excluding cases with extranodal extension); ③Closemargin \< 5 mm; ④Lymphovascular and/or perineural invasion; ⑤Invasion depth \> 5mm for T2 oral cavity cancer * Laboratory tests must meet the following criteria: ①Hematologic parameters (within 14 days without transfusion or blood products): a. Hemoglobin (Hb) ≥80 g/L; b.Absolute neutrophil count (ANC) ≥ 1.0 × 10⁹/L; c. Platelet count (PLT) ≥ 80 × 10⁹/L; ②Biochemical parameters: a. Bilirubin (BIL) \< 1.5 × upperlimit of normal (ULN); b.Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤ 2.5 × ULN; * Expected survival time ≥ 6 months; * Women of child bearing potential must have a negative pregnancy test (serum or urine) within 7 days prior to enrollment and agree to use reliable contraception during the study period; Male subjects must use reliable contraception from before treatment initiation until 120 days after the last dose of study drug * With PD-L1 immunohistochemistry testing * Participant voluntarily agrees to participate in this study and signs the informed consent form Exclusion Criteria: * Pregnancy or lactation, or intention to become pregnant during the study period. * Presence of active autoimmune disease or immunodeficiency, including but not limited to: myasthenia gravis, interstitial pneumonia, enteritis, autoimmune hepatitis, hypophysitis, vasculitis, nephritis, or hyperthyroidism. * Known human immunodeficiency virus (HIV) infection, history of autoimmune diseases, or history of organ transplantation. * Use of systemic immunosuppressive drugs within 2 weeks prior to initiation of study treatment, or anticipated need for systemic immunosuppressive therapy during the study treatment period. * Diagnosis of another malignancy within 3 years prior to enrollment. * History of Grade I or higher myocardial ischemia or myocardial infarction, severe arrhythmia, or ≥ Grade 2 congestive heart failure (New York Heart Association \[NYHA\] classification) within 6 months prior to enrollment. * Participation in another clinical trial or completion of another clinical trial within 4 weeks prior to enrollment. * Prior treatment of immunotherapy (including PD-1/PD-L1/CTLA-4 antibodies) or anti-EGFR agents. * Known or suspected allergy to the investigational product or any drug related to this trial. * Any other severe medical condition that, in the investigator's judgment, may compromise patient safety or interfere with the subject's ability to complete the study.