Condition: Head And Neck Neoplasms

This is a randomized, active-controlled, open-label study of pembrolizumab (Pembro) given prior to surgery and pembrolizumab in combination with standard of care radiotherapy (with or without cisplatin), as post-surgical therapy in treatment naïve participants with newly diagnosed Stage III/IVA, resectable, locoregionally advanced, head and neck squamous cell carcinoma (LA-HNSCC). Efficacy outcomes will be stratified by programmed cell death ligand 1 (PD-L1) combined positive score (CPS) status. The primary hypothesis is that pembrolizumab given before surgery and after surgery in combination with radiotherapy (with or without cisplatin) improves major pathological response and event-free survival compared to radiotherapy (with or without cisplatin) given after surgery alone.