PDCD1 and lung cancer: Several studies have reported the clinical importance of PD-L1 expression in lung cancer; the relationship between the tumour PD-L1 expression status and prognosis16, 17, and the response to immune checkpoint inhibitors such as anti-PD-1 antibodies (i.e. nivolumab18 and pembrolizumab19) and anti-PD-L1 antibodies (i.e. atezolizumab20 and durvalumab21).