Inclusion Criteria:  Major patient Metastatic non-small cell lung cancer Initiation of anti PDL1 therapy (NIVOLUMAB, PEMBROLIZUMAB or ATEZOLIZUAMB) in daily practice No objection made  Exclusion Criteria:  Autoimmune disease diagnosed prior to initiation of immune checkpoint inhibitor therapy. Previous immune-modulating therapy (including corticosteroid therapy greater than 10 mg/day) Patient with prior checkpoint inhibitor therapy Patient with a contraindication to immunotherapy Patient under legal protection Refusal to participate