Plasma-Adapted First-Line Pembro In NSCLC

This is an open label, single institution, prospective pilot study. The purpose of this research study is to determine if a blood test, collected at different times during treatment, can be used to detect early response in patients being treated with pembrolizumab for lung cancer and use that information to determine whether patients should continue treatment with pembrolizumab or switch treatment to pembrolizumab in combination with chemotherapy. -The research study procedures include screening for eligibility and study treatment including evaluations approximately every 3 weeks. The names of the study drugs involved in this study are: * Pembrolizumab * Platinum doublet chemotherapy, which may include the following: * Carboplatin and pemetrexed * Carboplatin and paclitaxel The name of the blood test: * InVision- Inivata * This blood test that will help study how participants respond to the study treatment. --- * Blood will be collected for this test at a few time points, both before and after participants receive treatment on study. * Participants will be on the research study for up to 12 months. * It is expected that about 40 people will take part in this research study.