Evaluating a Fasting-mimicking Diet in Combination With Immunotherapy in Patients With Non-small Cell Lung Cancer

This study is testing whether a fasting-mimicking diet (a special low-calorie diet designed to trick the body into a fasting state) can improve the effectiveness of immunotherapy for patients with stage IV non-small cell lung cancer. **You may be eligible if...** - You are 18 or older with newly diagnosed stage IV non-small cell lung cancer - Your tumor expresses high levels of PD-L1 (50% or more) and you qualify for single-agent pembrolizumab immunotherapy - Your performance status (ECOG) is 0, 1, or 2, meaning you can care for yourself - Your BMI is 19 or above - You have not yet started immunotherapy **You may NOT be eligible if...** - You have a specific gene mutation (like EGFR, ALK, ROS1) that would require targeted therapy instead - You have severe malnutrition or a condition that makes fasting dangerous - You have uncontrolled diabetes - You are already receiving cancer treatment Talk to your doctor to see if this trial is right for you.