Efficacy of pembrolizumab in patients with brain metastasis caused by previously untreated non-small cell lung cancer with high tumor PD-L1 expression

Objectives Pembrolizumab is recommended for patients with previously untreated non-small cell lung cancer (NSCLC) with a programmed death ligand 1 (PD-L1) tumor proportion score (TPS) of ≥1%. The KEYNOTE-024 study described the efficacy of pembrolizumab in patients with previously untreated NSCLC who had a PD-L1 TPS of at least 50 %. However, patients with untreated brain metastasis (BM) were excluded from many clinical trials. Therefore, we assessed the efficacy of pembrolizumab against BM of NSCLC with high tumor PD-L1 expression. Materials and Methods We retrospectively reviewed patients who received pembrolizumab as first-line treatment against NSCLC with PD-L1 TPS ≥ 50 % between March 2017 and September 2019. Treatment efficacy was compared between patients with (BM group) and without BM (non-BM group). In addition, the BM group was divided into patients who previously received treatment for BM before pembrolizumab (BM-T group) and those with no prior treatment for BM (BM-not T group). Results Eighty-seven patients (23 BM group and 64 non-BM group) were assessable for efficacy. No significant differences in patient characteristics were found between the BM and non-BM groups, but proportion of patients with stage IV at diagnosis was significantly higher in the BM group. Median progression-free survival (PFS) (6.5 months vs. 7.0 months) and overall survival (OS) (21.6 months vs. 24.6 months) did not significantly differ between the two groups. The response rate of BM was 70 %. The BM group was subdivided into 13 patients in the BM-T group and 10 patients in the BM-not T group. No significant differences in patient characteristics were found between the two groups, but maximum diameter of BM and proportion of patients with symptomatic BM were significantly greater in the BM-T group. PFS and OS did not significantly differ between the two groups. The median PFS of BM was 13.6 months in the BM-T group and 18.6 months in the BM-not T group. Conclusion Pembrolizumab may be effective for BM caused by previously untreated NSCLC with high PD-L1 tumor expression.