Assess Diversity of Gut Microbiome in Met NSCLC in Correlation to Tx & Adverse Effects

This study is looking at the diversity of gut bacteria (microbiome) in people with advanced or metastatic non-small cell lung cancer (NSCLC). Researchers want to understand how your gut bacteria may relate to how well immunotherapy or targeted therapy works and any side effects you experience. **You may be eligible if...** - You are 18 years old or older - You have been diagnosed with advanced or metastatic non-small cell lung cancer - You are eligible to receive immunotherapy drugs (such as pembrolizumab or nivolumab) or targeted therapy drugs (tyrosine kinase inhibitors) - You are willing to provide stool or blood samples for analysis **You may NOT be eligible if...** - Your doctor determines that you are too clinically unstable to participate safely Talk to your doctor to see if this trial is right for you.