Immunotherapy, principally represented by programmed death 1/programmed death ligand 1 (PD-1/PD-L1) inhibitors, has been approved worldwide as treatment for advanced non–small cell lung cancer (NSCLC) and has been hailed as an important addition to the treatment armamentarium for this population. In an unselected previously treated NSCLC population, response rates with single-agent immune checkpoint inhibitors (ICIs) range between 14% and 20%, with median overall survival (OS) of 10 to 12 months.
1-5 However, when this population is stratified by specific biomarkers, notably positive PD-L1 expression by immunohistochemical analysis, these outcomes improved, reaching up to 30% response with a median OS of 20 months,
3,5 in contrast to patients with negative or weak PD-L1 expression (1%-49% positive tumor cells, accounting for approximately 67% of the population) for whom response rates between 8% and 19% have been reported with median OS slightly below 10 months.
6 However, even within the PD-L1–positive stratum, the benefit with immunotherapy is not seen for the entire population, making the identification of biomarkers for patients likely to respond to ICI therapy a critical step in selecting the candidate population.