CDK inhibitor, CPTAC, EGFR mAb, HNSCC, combination immune checkpoint blockade, immune evasion, immunotherapy, predictive biomarker, proteogenomics, proteomics, Adult, Aged, Aged, 80 and over, Antineoplastic Agents, Immunological, ErbB Receptors, Female, Humans, Immunotherapy, Male, Middle Aged, Papillomavirus Infections, Proteogenomics, Proteomics, Squamous Cell Carcinoma of Head and Neck, Young Adult