PDCD1 and non-small cell lung carcinoma: Pembrolizumab, an anti-PD-1 monoclonal antibody, was approved by the US Food and Drug Administration (FDA) as a monotherapy first-line treatment of metastatic non-small cell lung cancer (NSCLC) with PD-L1 expression ≥ 1, and in combination with chemotherapy regardless of PD-L1 status [1,2,3,4].