Study of CTDNA Response Adaptive Immuno-Chemotherapy in Lung Cancer

This study is testing whether patients with advanced non-small cell lung cancer (NSCLC) who have detectable cancer DNA in their blood after starting immunotherapy (pembrolizumab) would benefit from adding chemotherapy to their treatment. The study uses a blood test called ctDNA (circulating tumor DNA) to guide treatment decisions. **You may be eligible if...** - You are 18 or older - You have advanced or metastatic NSCLC with a PD-L1 score of 50% or higher (meaning your cancer is more likely to respond to immunotherapy) - Your cancer does NOT have EGFR or ALK mutations - You have recently started pembrolizumab (immunotherapy) as your first cancer treatment - You have detectable cancer DNA in your blood at 6 weeks into immunotherapy **You may NOT be eligible if...** - You have symptomatic brain metastases requiring high-dose steroids - You have an autoimmune condition requiring immunosuppressive drugs - You are pregnant or breastfeeding - You are receiving another cancer treatment at the same time Talk to your doctor to see if this trial is right for you.