Noordhof AL, Damhuis RAM, Hendriks LEL, et al. - Researchers undertook this real-world retrospective population-based study to ascertain if survival on first-line pembrolizumab differs for patients with stage IV lung adenocarcinoma with a high programmed death-ligand 1 (PD-L1) status with or without a KRAS (Kirsten rat sarcoma) mutation. They compared this survival using real-world data. The Netherlands Cancer Registry was used to identify patients having stage IV lung adenocarcinoma with PD-L1 expression ≥50%, managed with first-line pembrolizumab. A KRAS mutation was present in 388 (57%) of 595 patients. For patients carrying a KRAS mutation vs those who did not, the estimated median overall survival was 19.2 months vs 16.8 months, respectively. Independent prognostic factors, as identified in multivariable analysis, included WHO performance score, number of organs with metastases and PD-L1 percentage. Overall, a similar survival was observed between patients with KRAS mutated vs KRAS wild-type lung adenocarcinoma treated with first-line pembrolizumab monotherapy. This indicates no prognostic worth of KRAS with respect to treatment with pembrolizumab.