KEYNOTE-042 and the role for single agent pembrolizumab in patients with PD-L1 tumor proportion score 1–49%

Immunotherapy with monoclonal antibodies against programmed death-1 (PD-1) or its ligand (PD-L1) were approved for previously treated advanced non-small cell lung cancer (NSCLC) based on the results from four randomized trials showing improved survival compared to standard therapy with docetaxel (1-4). in the phase 1 study with the anti-PD-1 antibody pembrolizumab in previously treated NSCLC, the response rate and median progression-free survival (PFS) for patients with PD-L1 proportion score of ≥50% were 45.2% and 6.3 months respectively, with median PFS of 6.1 months for the 99 previously treated patients and 12.5 months for the 20 previously untreated patients (5). Therefore, the next logical step was to evaluate the role of pembrolizumab in previously untreated patients with PD-L1 score of ≥50%, where the efficacy was comparable to historical data on first-line platinum-based combination chemotherapy with or without maintenance chemotherapy (6-9).