Can a simple blood test predict cancer treatment success?

This observational study is collecting blood samples and medical images from 200 people with several types of solid tumors (like lung, head and neck, and esophageal cancers) who are receiving immunotherapy and radiation as part of their standard care. Researchers want to see if changes in immune cells in the blood or patterns in scans can predict how well the treatment works or if side effects occur. The goal is to find reliable markers that could guide future treatment decisions.