Fiber-Boost Randomized Controlled Trial

This study — called Fiber-Boost — is testing whether adding a high-fiber diet supplement to standard immunotherapy (PD-1/PD-L1 checkpoint inhibitor) can improve outcomes for people with advanced non-small cell lung cancer (NSCLC). Research suggests gut bacteria (which are fed by dietary fiber) may influence how well immunotherapy works, and this trial tests that idea in patients. **You may be eligible if...** - You are 18 or older with a confirmed diagnosis of advanced or recurrent non-small cell lung cancer - Your cancer strongly expresses a protein called PD-L1 (≥50%), meaning immunotherapy alone is recommended - You do not have certain genetic mutations (EGFR, ALK, ROS1, etc.) that would require targeted therapy instead - This would be your first systemic treatment for advanced disease - You are in reasonably good physical condition (ECOG 0–2) with adequate blood counts, liver, and kidney function **You may NOT be eligible if...** - You have had another cancer within the past 3 years (with some exceptions for low-risk cancers) - You have recently taken antibiotics (within 10 days of starting treatment) - You are on immune-suppressing medications (e.g., high-dose steroids, methotrexate) - You have had an organ or tissue transplant - You have active autoimmune disease requiring treatment - You have uncontrolled diabetes or serious cardiovascular disease - You are currently taking a fiber supplement (OptiFibre or similar) - You are pregnant or breastfeeding Talk to your doctor to see if this trial is right for you.