First-Line Pembrolizumab Monotherapy for Advanced Non-Small Cell Lung Cancer: A Multicenter Real-World Study from Vietnam.

[BACKGROUND] This study aimed to evaluate the effectiveness and safety of first-line pembrolizumab monotherapy in patients with advanced non-small cell lung cancer (NSCLC) in real-world clinical practice in Vietnam.

[METHODS] We performed a multicenter retrospective cohort study of patients with locally advanced or metastatic NSCLC who received first-line pembrolizumab monotherapy in Vietnam between January 2018 and August 2024. The primary endpoints were progression-free survival (PFS), overall survival (OS), and safety profile.

[RESULTS] A total of 73 patients were included, with a median age of 69 years (range, 47-92). Most patients had good performance status (ECOG PS 0-1, 75.3%) and high PD-L1 expression (TPS ≥ 50%, 86.3%). The overall response rate was 60.3%, and the disease control rate was 79.5%. Median PFS was 11.3 months (95% CI, 6.9-15.8), and median OS was 25.4 months (95% CI, 20.8-30.0). Multivariate analysis identified never-smoking status (HR 3.14, 95% CI 1.16-8.50; = 0.024), squamous histology (HR 4.09, 95% CI 1.18-14.17; = 0.026), and low PD-L1 expression (TPS 1-49%) (HR 3.67, 95% CI 1.14-11.78; = 0.029) as independent predictors of inferior overall survival. Immune-related adverse events, including pneumonitis, hepatitis, nephritis, fever, skin reactions, and myositis, were mostly mild and manageable, with grade 3 toxicity occurring in only 4.2% of patients. Better survival was observed in patients with high PD-L1 expression and non-squamous histology. However, the association with non-squamous histology should be interpreted with caution due to the very small number of squamous cases.

[CONCLUSIONS] First-line pembrolizumab monotherapy demonstrated favorable effectiveness and acceptable safety in patients with advanced NSCLC in real-world clinical practice in Vietnam. Clinical outcomes were particularly favorable in patients with high PD-L1 expression, non-squamous histology, and a history of smoking. Nevertheless, the survival benefit associated with non-squamous histology should be interpreted cautiously, given the limited number of patients with squamous histology. These findings support the use of pembrolizumab monotherapy in selected patient populations within resource-limited settings.