Clinical Outcomes of First-Line Pembrolizumab Monotherapy in Advanced NSCLC With PD-L1 Tumor Proportion Score of 1% to 49%: A Retrospective Multicenter Study

Introduction: This study aimed to evaluate the real-world clinical outcomes of pembrolizumab monotherapy in patients with advanced NSCLC with programmed death-ligand 1 (PD-L1) tumor proportion score (TPS) of 1% to 49%. Methods: A multicenter retrospective analysis was conducted for outcomes of 114 patients with stages II to IV or recurrent NSCLC and PD-L1 TPS of 1% to 49%, who received first-line pembrolizumab monotherapy. Results: The median progression-free survival (PFS) was 5.6 months, with 6-month and 60-month PFS rates of 47.4% and 5.1%, respectively. The median overall survival (OS) was 15.8 months, with 24-month and 60-month OS rates of 34.8% and 17.0%, respectively. The objective response rate was 36.9%, and the disease control rate was 60.4%. Multivariate analysis identified liver metastasis as a significant negative prognostic factor for PFS, but a high neutrophil-to-lymphocyte ratio (NLR) revealed a trend toward worse PFS. Similarly, liver metastasis, high NLR, and poor performance status were significantly associated with worse OS. Grade more than or equal to 3 immune-related adverse events were observed in 20.2% of patients, with pneumonitis being the most common. Those with a history of interstitial lung disease had a higher incidence of severe pneumonitis than those without. Treatment discontinuation due to disease progression occurred in 65.8% of patients, whereas 23.7% discontinued due to adverse events. Conclusions: First-line pembrolizumab monotherapy demonstrated moderate efficacy and acceptable safety in patients with advanced NSCLC with PD-L1 TPS of 1% to 49%. Liver metastasis, high NLR, and poor performance status were identified as prognostic factors.