Effectiveness of Second-Line Pembrolizumab Monotherapy for the Treatment of Nonsmall Cell Lung Cancer: A Retrospective-Single Institution Study of 52 Vietnamese Patients.

Background: Our aim was to demonstrate the efficacy and safety of pembrolizumab monotherapy as second-line treatment in Vietnamese nonsmall cell lung cancer (NSCLC) patients. Methods: We performed a single-center retrospective study of patients with advanced NSCLC who received pembrolizumab as second-line therapy at the Vietnam National Cancer Hospital between January 2017 and October 2023. The primary endpoints were overall survival (OS) and tumor response. Results: A total of 52 patients were included. Adenocarcinoma was observed in 43 of 52 cases (82.7%), and 40.4% of patients had PD-L1 expression in at least 50% of tumor cells. Median body weight was 57 kg (range, 45-80), and 73.1% of patients received pembrolizumab at a dose of 100 mg/3 weeks, with a median dose of 1.9 mg/kg/3-weeks (range, 1.3-4.3). The overall response rate and disease control rate were 26.9% and 51.9%, respectively. Median PFS was 6.5 months (95% CI, 3.3-9.7), and 1-year and 2-year PFS rates were 28.5% and 15.9%, respectively. Median OS was 12.0 months (95% CI, 9.8-14.2); 1-year, 2-year, and 3-year OS rates were 53.1%, 22.3%, and 8.5%, respectively. ECOG status and number of organs metastases were significantly associated with PFS and OS in the multivariate analysis. No adverse events of grades 3 to 4 were reported during the treatment. Conclusions: Second-line pembrolizumab has a good disease control rate and prolonged survival and is a viable option for the treatment of Vietnamese NSCLC patients. Further clinical studies are necessary to determine the effectiveness of administering a low dose of pembrolizumab in this setting, particularly in Asian population.