First-Line Treatment of Non-Small-Cell Lung Cancer (NSCLC) with Immune Checkpoint Inhibitors

Treatment of advanced-stage or metastatic non-small-cell lung cancers (NSCLCs) without EGFR mutations or ALK rearrangements, which can now be treated with molecularly targeted therapies, had been based on cytotoxic chemotherapy for a long time. Immune checkpoint inhibitors (ICIs), notably antibodies directed against programmed cell-death protein-1 (PD-1) and its ligand (PD-L1) have transformed therapeutic standards in thoracic oncology. These ICIs are now the reference second-line treatment and numerous phase III trials have examined their efficacy in treatment-naïve patients. First-line pembrolizumab monotherapy was validated for patients with ≥ 50% of tumor cells expressing PD-L1; pembrolizumab, atezolizumab, and nivolumab have obtained good outcomes in combination with chemotherapy or another immunotherapy. However, in this context, other phase III trials yielded negative findings for nivolumab alone (CheckMate-026) or in combination (MYSTIC trial). Biomarkers, such as PD-L1 and the tumor mutation burden (TMB), enable better selection of patients who should benefit the most from first-line ICI use.