Immunotherapy’s new challenge: identification of predictive biomarkers for tumor response

Immune checkpoint inhibitors (ICI) targeting programmed cell death protein 1 (PD-1)/ programmed cell death protein ligand 1 (PD-L1) pathway are a promising therapeutic option in patients with non-small cell lung cancer (NSCLC) (1). However, PD-L1 immunohistochemistry (IHC) assessment has a non-optimal predictive value of response. Main reasons are tumor heterogeneity, no standardized staining assessment with different primary antibodies, variable positive thresholds and interobserver variability. A major challenge for these immunotherapies is to improve patient selection. PD-L1 expression does not seem to be sufficient, and other immunologic or non-immunologic markers may influence responses to ICI.