Pembrolizumab as the first-line monotherapy for non-small-cell lung cancer with a low programmed death ligand 1 threshold.

Pembrolizumab monotherapy has been demonstrated as a first-line therapy for non-small-cell lung cancer (NSCLC) patients with a programmed death ligand 1 (PD-L1) tumor proportion score (TPS) of ≥50%; however, the clinical efficacy is limited by the unreasonable threshold of the TPS. A recent study published by Mok et al. (Lancet 393:1819-1830, 2019) showed that pembrolizumab monotherapy could also be extended as an effective first-line therapeutic strategy for NSCLC patients with low TPS. However, this needs to be further evaluated in detail after considering the following issues. In Mok's report, the survival curves were much lower in a pembrolizumab-treated group in the first 6 months of treatment compared with a chemotherapy group. These contradictory findings might have been due to anecdotal occurrences of rapid progression, especially hyperprogressive disease.