Pembrolizumab plus Chemotherapy in Lung Cancer

To the Editor: In the KEYNOTE-189 trial, Gandhi et al. (May 31 issue)¹ compared pembrolizumab plus chemotherapy with chemotherapy alone in patients with untreated metastasic non–small-cell lung cancer. They concluded that patients with a tumor proportion score of 50% or more for programmed death ligand 1 (PD-L1) showed a greater benefit with the combination regimen. Statistical interaction should be calculated to check the reliability of that suggested difference.² No interaction was found between subgroups of patients with a PD-L1 tumor proportion score of 1 to 49% and subgroups with a score of 50% or more (P>0.10)³; confidence intervals are mostly . . .