Pembrolizumab Plus Chemotherapy for Metastatic NSCLC With Programmed Cell Death Ligand 1 Tumor Proportion Score Less Than 1%: Pooled Analysis of Outcomes After Five Years of Follow-Up

BACKGROUND: We report long-term outcomes from a pooled analysis of patients with previously untreated metastatic NSCLC with programmed cell death ligand 1 (PD-L1) tumor proportion score (TPS) less than 1% enrolled in phase III 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 People's Republic of 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). The median follow-up was 60.7 (range, 49.9‒72.0) months. Pembrolizumab plus chemotherapy improved overall survival (hazard ratio, 0.64; 95% confidence interval [CI]: 0.51‒0.79) and progression-free survival (hazard ratio, 0.66; 95% CI: 0.54‒0.81) versus chemotherapy. The 5-year overall survival rates (95% CI) were 12.5% (8.6%‒17.3%) versus 9.3% (5.6%‒14.1%). Grades 3 to 5 treatment-related adverse events occurred in 59.1% of patients for pembrolizumab plus chemotherapy and 61.3% for chemotherapy. CONCLUSION: With approximately 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 less than 1%. These results continue to support pembrolizumab plus chemotherapy as a standard of care in this patient population. CLINICALTRIALS: gov, NCT02578680 (KEYNOTE-189 global), NCT03950674 (KEYNOTE-189 Japan extension), NCT02775435 (KEYNOTE-407 global), NCT03875092 (KEYNOTE-407 People's Republic of China extension).