Challenges of predicting immune checkpoint therapy responders in lung cancer

Non-small cell lung cancer (NSCLS) is the leading cause of cancer related death worldwide (1) and usually diagnosed in an already metastasized state, hence leaving systemic therapy as the preferred treatment with only a minority of patients eligible for targeted therapies. Recent developments from the so-called immune checkpoint blockade (ICB) or immunotherapy, mainly targeting programmed death-1 (PD-1) receptor or the ligand (PD-L1) (2-5), offer improved outcome of patients following relapse after platinum-based chemotherapy or even as first-line therapy (6,7). However, patient selection is a critical step and the development of predictive biomarkers is of utmost importance.