**Study Summary** This study investigates how well *immune maintenance therapy* works for patients with head and neck cancer. The cancer type is called *squamous cell carcinoma*, which affects the skin-like cells in the head and neck area. The study focuses on patients whose cancer is *locally advanced*, meaning it hasn't spread far. These patients have already had a special kind of treatment called *neoadjuvant immunotherapy* with chemotherapy. This treatment is given before surgery to shrink tumors. The main goal is to see if continuing with immune therapy after surgery helps keep the cancer from coming back. The study also checks if this ongoing treatment is safe for the patients. **Key Points:** - **Duration & Visits:** The study may require multiple visits over a period to monitor health and treatment. - **Compensation:** Information about any compensation for participation might be provided. - **Risks & Benefits:** Potential risks and benefits will be clearly explained to all participants. *Eligibility*: Participants must be 18-80 years old, in good physical condition, and have non-metastatic cancer confirmed by tests. Exclusions include having other active diseases or infections, or recent participation in other trials.