Predictive biomarkers of response to PD-1/PD-L1 immune checkpoint inhibitors in non-small cell lung cancer

Inhibitors of the programmed cell death 1 (PD-1) pathway show the potential to substantially increase the efficacy of therapy for various malignancies, including non-small cell lung cancer (NSCLC). At the same time, substantial effort has been invested in finding biomarkers predicting which patients will respond best to this immune checkpoint inhibition. PD-L1 expression in tumor cells and the tumor microenvironment, genetic alterations and mutational load in tumor cells, and pre-existing immunity and its enhancement during treatment through tumor-infiltrating immune cells have been associated with outcomes of immune checkpoint inhibition. Here, we review the reported predictive biomarkers of response to PD-1 pathway immune checkpoint inhibitors in NSCLC, mainly focusing on results obtained with clinical trials.