Exploratory Study of Early Biomarkers Allowing Dynamic Assessment of Response to Treatment in Cancers of the Head and Neck

This study is collecting blood samples from people with recurrent, advanced, or metastatic head and neck cancer who are receiving immunotherapy, to search for early blood-based markers (called biomarkers) that could predict how well the immunotherapy is working — potentially allowing doctors to monitor response without repeated biopsies. **You may be eligible if...** - You are 18 years or older - You have a confirmed head and neck cancer that has come back, spread, or is not curable with standard treatments - You are currently receiving immunotherapy - You can give consent and provide blood samples at multiple time points **You may NOT be eligible if...** - You are unable to undergo regular blood sample collection - You are pregnant Talk to your doctor to see if this trial is right for you.