Pembrolizumab monotherapy has been shown to significantly prolong survival in metastatic non-small cell lung cancer (NSCLC) compared to platinum-doublet chemotherapy. Martin Reck, MD, PhD, German Center of Lung Research, Grosshansdorf, Germany, discusses the results of the Phase III KEYNOTE-598 trial (NCT03302234) of pembrolizumab alone or combined with ipilimumab in patients with metastatic NSCLC, designed to expand on this finding. 568 patients with a PD-L1 tumor proportion score (TPS) ≥50% were included in the trial and followed-up for a median of 20 months. The results showed that adding ipilimumab caused more adverse events than pembrolizumab-placebo, causing a higher rate of treatment discontinuation. Additionally, no benefit was seen when ipilimumab was added to pembrolizumab. The median overall survival, progression-free survival and duration of response was comparable in the pembrolizumab-ipilimumab arm and the pembrolizumab placebo arm. This interview took place during the IASLC World Conference on Lung Cancer (WCLC) virtual meeting 2021.