Pembrolizumab Plus Chemotherapy for Metastatic Non–Small-Cell Lung Cancer With Programmed Cell Death Ligand 1 Tumor Proportion Score Less Than 1%: Pooled Analysis of Outcomes After 5 Years of Follow-Up

Background We report long-term outcomes from a pooled analysis of patients with previously untreated metastatic non‒small-cell lung cancer (NSCLC) with programmed cell death ligand 1 (PD-L1) tumor proportion score (TPS) <1% enrolled in phase 3 studies of pembrolizumab plus chemotherapy versus placebo plus chemotherapy. Methods This exploratory pooled analysis included individual patient data from the KEYNOTE-189 global (NCT02578680) and Japan extension (NCT03950674) studies of metastatic nonsquamous NSCLC without EGFR or ALK alterations and the KEYNOTE-407 global (NCT02775435) and China extension (NCT03875092) studies of metastatic squamous NSCLC. Patients received pembrolizumab or placebo plus pemetrexed and cisplatin or carboplatin in KEYNOTE-189 and pembrolizumab or placebo plus carboplatin and paclitaxel or nab-paclitaxel in KEYNOTE-407. PD-L1 TPS was centrally assessed using PD-L1 IHC 22C3 pharmDX (Agilent Technologies, Carpinteria, CA). Results Overall, 442 patients were included in this analysis (pembrolizumab plus chemotherapy, n=255; chemotherapy, n=187). Median follow-up was 60.7 (range, 49.9‒72.0) months. Pembrolizumab plus chemotherapy improved overall survival (OS; hazard ratio [HR], 0.64; 95% CI, 0.51‒0.79) and progression-free survival (HR, 0.66; 95% CI, 0.54‒0.81) versus chemotherapy. Five-year OS rates (95% CI) were 12.5% (8.6%‒17.3%) versus 9.3% (5.6%‒14.1%). Grade 3‒5 treatment-related adverse events occurred in 59.1% of patients for pembrolizumab plus chemotherapy and 61.3% for chemotherapy. Conclusion With ∼5 years of follow-up, pembrolizumab plus chemotherapy provided clinically meaningful and durable improvements in survival outcomes versus chemotherapy alone in patients with previously untreated metastatic NSCLC with PD-L1 TPS <1%. These results continue to support pembrolizumab plus chemotherapy as a standard of care in this patient population.