Study of Longitudinal Plasma PD-L1 Testing With Immunotherapy in Lung Cancer

Inclusion Criteria: 1. All patients with a diagnosis of stage IV or inoperable stage IIIB NSCLC without planned primary radiation therapy undergoing anti-PD-1/L1 based ICI treatment. 2. Chemo-immune or dual anti-PD-1/L1 with anti-CTLA-4 based regimens are eligible as long as receiving an anti-PD-1/L1 monoclonal antibody. 3. A documented informed consent will be obtained prior to inclusion in the study. All discussions with patients will be held in strictest confidence and out of earshot of the general public. Patients will be fully informed that their participation in the study is voluntary. Patients may decline to be part of the study. Their decision to participate in the study will not affect the care they receive. Exclusion Criteria: 1. No anti-PD-1/L1 monoclonal antibody treatment. 2. Planned primary radiation therapy. 3. Small-cell lung cancer histology.