Phase 2 study of first‐line pembrolizumab monotherapy in elderly patients with non‐small‐cell lung cancer expressing high PD‐L1

BACKGROUND: Pembrolizumab is the recommended first‐line therapy for patients with advanced non‐small‐cell lung cancer (NSCLC) and a programmed death ligand‐1 (PD‐L1) tumor proportion score (TPS) of ≥50% without driver mutations. However, its efficacy and safety for patients ≥75 years have not been prospectively investigated; this was the aim of this study. METHODS: This multicenter and open‐label single‐arm phase II study was conducted at 12 institutions. Chemotherapy‐naïve patients with advanced NSCLC and a PD‐L1 TPS of ≥50% without EGFR mutations or translocation of the ALK received pembrolizumab every 3 weeks. The primary endpoint was progression‐free survival (PFS) with a threshold of 4.3 months. The secondary endpoints were overall survival (OS), objective response rate (ORR), disease control rate (DCR), safety, and quality of life. RESULTS: Twenty‐six patients were enrolled between October 2017 and March 2020. The median PFS was 9.6 (95% confidence interval [CI] 2.1–20.6) months. The lower limit of the 95% CI did not exceed the target. The median OS was 21.6 months. The ORR and DCR were 41.7% and 70.8%, respectively. The proportion of patients with grade ≥3 treatment‐related adverse events was 15.4%. The quality of life score did not change significantly during treatment. CONCLUSION: While this study showed that pembrolizumab was a tolerable treatment for elderly patients, the safety requires further confirmation in a larger study. Although the primary endpoint, the median PFS (9.6 months), was slightly shorter than that (10.3 months) of the previous phase III study (KEYNOTE‐024 study), the median PFS did not achieve the expected value.