Efficacy of Lower Fixed Dose Pembrolizumab in the Treatment of Non-Small Cell Lung Cancer Patients in a Lower-Middle Income Country: Jordan Experience

Background: Pembrolizumab was approved as first line treatment of advanced non-small cell lung cancer (NSCLC) at standard dose of 200mg every 3 weeks. We aim to assess the efficacy of a lower fixed dose of 100mg and review the Jordanian experience in first line setting. Methods: We conducted a retrospective study of 88 NSCLC patients, including 27 who received low fixed dose pembrolizumab (Pem100) and 61 received standard fixed dose (Pem200) from September 2016 to February 2022. Results: Objective response rate was (48.8%), including (5.6%) with complete response, and (43.2%) with partial response. The median progression free survival (PFS) and median overall survival (OS) for this Jordanian population were consistent with published clinical trials; 8.00 months (95% CI, 7.19 to 8.80) and 17.48 months (95 CI, 15.53 to 19.44), respectively. The PFS and OS were not statistically different between the Pem100 and Pem200 groups (8.00 vs. 8.00 months, p=0.73, and 17.02 vs 17.60 months, p=0.66, respectively). PFS and OS were significantly affected by the programmed cell death ligand (PD-L1) tumor proportion score (TPS) (12.40 vs. 8.00 vs. 5.80 months, p<0.001, and 22.70 vs. 16.47 vs. 12.71 months, p<0.001, in TPS ≥ 50% vs. TPS 1-49% vs. TPS < 1%, respectively). OS was not statistically different according to age, gender, histology, or smoking status. Conclusion: Lower fixed dose pembrolizumab (100mg 3-weekly) appears to be effective in first line NSCLC. A randomized trial should be done to investigate this low dose with significant cost reduction potential.