Pointed Progress in Second-Line Advanced Non-Small-Cell Lung Cancer: The Rapidly Evolving Field of Checkpoint Inhibition

Purpose Non-small-cell lung cancer (NSCLC) is globally prevalent and associated with high rates of mortality. Immune checkpoint pathways are often exploited by tumors to evade immunity-mediated destruction, and checkpoint inhibitors can reactivate tumor-related immune responses. This review considers available clinical evidence for the use of checkpoint inhibitors in the treatment of second-line advanced NSCLC. Methods Our systematic search revealed 20 clinical trials evaluating checkpoint inhibitors in the second-line setting, three of which were randomized trials comparing programmed cell death protein 1 and programmed death ligand 1 (PD-L1) inhibitors to docetaxel, the current standard of care in this setting. Results A randomized phase II trial comparing the PD-L1 inhibitor atezolizumab to docetaxel did not demonstrate improved survival for atezolizumab in patients overall, although a trend toward improved survival with increased PD-L1 expression was apparent. Twin phase III trials showed significantly improved survival for the programmed cell death protein 1 inhibitor nivolumab compared with docetaxel in patients with both squamous and nonsquamous disease. PD-L1 expression correlated with improved survival in patients with nonsquamous disease, and patients with low levels of PD-L1 expression (< 10%) and those with EGFR mutations are unlikely to benefit. Checkpoint inhibitor therapy is generally well tolerated and associated with low rates of grade 3 or 4 adverse events compared with standard care. Conclusion Level 1 evidence exists to support the use of nivolumab as second-line treatment of patients with squamous advanced NSCLC, as well as in select patients with nonsquamous disease. Benefits remain unknown in patients with targetable driver mutations, and use of PD-L1 expression to guide therapy remains controversial. Results from ongoing randomized trials evaluating biomarkers and other checkpoint inhibitors will further our understanding of this rapidly evolving area of oncology. (C) 2016 by American Society of Clinical Oncology