Abstract
Unleashing the potential of immune system to fight cancer has become one of the main promising treatment modalities for advanced non-small cell lung cancer (NSCLC). The knowledge of numerous factors that come into play in the cancer-immunity cycle provide a wide range of potential therapeutic targets, including monoclonal antibodies that inhibits the programmed death-1 (PD-1) checkpoint pathway. Over the last two years, nivolumab, pembrolizumab and atezolizumab received approval for treatment of pretreated advanced NSCLC, and more recently, immunotherapy with pembrolizumab is the new standard of care as first-line in patients with high levels of programmed death-ligand 1 (PD-L1) expression. Selection of patients is mandatory and PD-L1 is the only biomarker currently available in clinical practice. However, PD-L1 staining is an imperfect marker, whose negativity does not exclude a response to immunotherapy, as well as the roughly half of patients are "not-responders" despite high tumor PD-L1 levels. The right cut-off, the differences among various immune checkpoint inhibitors and among various antibody clones, and a not trivial activity reported even in PD-L1 negative tumors are questions still open. New biomarkers beyond to PD-L1 assays as well as new strategies, including combination of immune checkpoint inhibitors are under investigation.