Postoperative CCRT Followed by Immunotherapy in High-Risk LA HNSCC

This study is testing whether adding an immunotherapy drug (a PD-L1 or PD-1 inhibitor) after surgery and radiation plus chemotherapy improves outcomes for patients with high-risk head and neck squamous cell carcinoma (cancer of the mouth, throat, or voice box). **You may be eligible if...** - You have confirmed squamous cell carcinoma of the oral cavity, throat, voice box, or related areas - Your cancer has one or more high-risk features (such as close surgical margins, spread beyond lymph nodes, or cancer invasion of nerves or blood vessels) - Your tumor expresses PD-L1 (a protein marker) with a combined positive score greater than 1 - You are in good general health (ECOG 0-1) and have adequate organ function - Pregnancy test is negative (if applicable) **You may NOT be eligible if...** - You have another active cancer (except cured skin cancer, cervical carcinoma in situ, or superficial bladder cancer) - You have an active infection - You have contraindications to immunotherapy or chemoradiotherapy Talk to your doctor to see if this trial is right for you.