Circulating Tumor DNA Alterations in Non-small Cell Lung Cancer Patients Treated With Pembrolizumab

The purpose of this study is to learn how to use blood tests to better predict how patients with non-small cell lung cancer, who are taking pembrolizumab for cancer treatment, will respond to treatment with pembrolizumab, and to understand how the immune system and cancer interact. Tests will be performed on tumor tissue and blood samples, and imaging assessments will be reviewed in order to monitor how well each patient responds to treatment. This is an observational study, so participants will not receive cancer treatment, other than the treatment received as standard of care.