Cetuximab Plus Dalpicilib in Patients With HPV Negative, PD-1 Resistant R/M HNSCC

Inclusion Criteria: * Age 18-75 years, both sexes. * Patients with histologically confirmed post-surgical recurrent/metastatic or locally advanced inoperable surgically resectable squamous cell carcinoma of the head and neck with measurable lesions (spiral CT scan ≥ 10 mm, meeting RECIST 1.1 criteria). * Have received at least 1 cycle of prior PD-1 immunotherapy with imaging confirmation of progression or clinician determination of no continued benefit from treatment; provided that this is completed at least 4 weeks prior to the first dose of study drug and all associated toxic events have returned to normal or grade I or less as defined by CTCAE 4.03 classification. * HPV viral testing determined to be negative, using the IHC method. * Availability of tumor tissue (paraffin specimens less than 2 years old or fresh tumor tissue) for detection of PD-L1 and CDK4-related genes. * ECOG score of 0 or 1. * Expected survival of ≥ 12 weeks. * Normal major organ function within 2 weeks prior to treatment, i.e., meeting the following criteria：Bone marrow function: hemoglobin ≥ 100 g/L without transfusion or colony-stimulating factor support therapy, white blood cell count ≥ 4.0\*10\^9/L or neutrophil count ≥ 2.0\*10\^9/L, and platelet count ≥ 100\*10\^9/L; Liver: serum total bilirubin level ≤ 1.5 times the upper limit of normal, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤ 1.5 times the upper limit of normal; Renal: blood creatinine level below 1.5 times the u…