Compare Radiotherapy Plus Nimotuzumab Versus Radiotherapy Alone in Platinum-ineligible Patients With Locoregionally Advanced Head and Neck Squamous Cell Carcinoma

Inclusion Criteria: * Eligible subjects must meet all of the following: * Age ≥18 years. * Histologically confirmed stage III-IVB (AJCC 8th edition) head and neck squamous cell carcinoma (including cancers of the oral cavity, oropharynx, hypopharynx, and larynx). * Unsuitable for surgical treatment (defined as: due to patient condition or tumor factors \[T3-4 N0-3 M0, or T1-2 N2-3 M0\] or medical reasons, surgery is not feasible; or an R0 resection is not achievable). * Suitable for definitive radiotherapy with curative intent. * At least one of the following reasons for being unsuitable for cisplatin-based chemotherapy: * Age ≥65 years and, in the investigator's judgment, unable to tolerate chemotherapy; * ECOG Performance Status \>2 (if this criterion is met, the ECOG criterion listed below may be waived); * Renal dysfunction: creatinine clearance (CrCl) \<50 mL/min (Cockcroft-Gault) (if this criterion is met, the renal function criterion listed below may be waived); * Severe tinnitus or hearing loss (requires a hearing aid or audiometry shows ≥25 dB loss at two consecutive frequencies); * Peripheral neuropathy \> Grade 1; * Inability to receive intravenous hydration (e.g., due to cardiac dysfunction) or other comorbidities, per investigator's judgment. * Provide tumor tissue, whenever possible, for EGFR testing; for oropharyngeal cancer, provide tissue for HPV/p16 testing if feasible (no need to retest if previously tested). * ECOG Performance Status 0-1 (or Karnofsky Performance Status ≥80). * At least one measurable lesion per RECIST 1.1. * Expected survival ≥6 months. * Adequate hematologic function: WBC ≥4×10\^9/L; absolute neutrophil count ≥1.5×10\^9/L; platelets ≥100×10\^9/L; hemoglobin ≥90 g/L. * Adequate renal function: serum creatinine ≤1.5×ULN or CrCl ≥60 mL/min (Cockcroft-Gault): * Female CrCl = (140 - age) × weight (kg) × 0.85 / (72 × S\_cr \[mg/dL\]) * Male CrCl = (140 - age) × weight (kg) × 1.00 / (72 × S\_cr \[mg/dL\]) * Adequate liver function: total bilirubin ≤1.5×ULN; AST ≤2.5×ULN; ALT ≤2.5×ULN. * Voluntary participation: signed written informed consent and ability to comply with visits and procedures. Exclusion Criteria: * Any of the following excludes enrollment: * Receipt of a PD-1 inhibitor, EGFR monoclonal antibody, EGFR-TKI, or anti-angiogenic agent within 4 weeks prior to enrollment. * Participation in another interventional clinical trial within 30 days prior to screening. * History of other malignancy (except cured basal cell carcinoma of the skin). * History of primary immunodeficiency. * Uncontrolled comorbid conditions (e.g., congestive heart failure, severe pulmonary disease, severe liver disease, psychiatric illness). * Known HIV infection, or active viral hepatitis or active tuberculosis. * Major surgery within 90 days before first study treatment, or planned surgery during the study. * Known allergy to nimotuzumab or its excipients. * Deemed unsuitable to participate by the investigator. * Unwilling or unable to sign informed consent. * Receipt of a live vaccine within 30 days before first dose.