Wakuda K, Yabe M, Kodama H, et al. - Via this retrospective review, researchers examined whether pembrolizumab has efficacy against brain metastasis (BM) of non-small cell lung cancer (NSCLC) with high tumor programmed death ligand 1 (PD-L1) expression. Participants were treated with pembrolizumab as first-line therapy against NSCLC with PD-L1 tumor proportion score ≥ 50 % between March 2017 and September 2019. In patients with (BM group) vs without BM (non-BM group), treatment efficacy was compared. The BM group was split into patients who previously underwent therapy for BM prior to pembrolizumab (BM-T group) and those with no previous therapy for BM (BM-not T group). Between BM group and non-BM group, there was no significant difference in median progression-free survival (PFS) and overall survival. In the BM-T group and in the BM-not T group, the median PFS of BM was estimated to be 13.6 months and 18.6 months, respectively. Findings are indicative of the likely effectiveness of pembrolizumab against BM caused by previously untreated NSCLC with high PD-L1 tumor expression.