Inclusion Criteria:  Adult ≥18 years old Patient diagnosed with Stage IV NSCLC (de novo or earlier stage progression to stage IV) Absence of oncogene activating mutations eligible patients to targeted therapy (EGFR, ALK) Cohort A: Received first line treatment with pembrolizumab monotherapy Cohort B: Received first line treatment with chemotherapy and pembrolizumab combination therapy Cohort C: Received first line treatment with chemotherapy doublet  Exclusion Criteria:  Prior anti-cancer therapy for actual stage IV NSCLC Critical data missing (e.g., PD-L1 status, baseline millimetric imaging, first evaluation millimetric imaging) Patients participating in other clinical trials that modify the standard of care