Pneumonitis in Older Patients With Non-squamous Non-small Cell Lung Cancer Treated With Pembrolizumab and Pemetrexed

BACKGROUND/AIM: Pembrolizumab combined with pemetrexed is efficacious in older patients with metastatic non-squamous non-small cell lung cancer (NSCLC) and a PD-L1 tumor proportion score (TPS) of <50%. However, treatment-related pneumonitis is concerning, and its impact on clinical outcomes is not fully understood. In this study, we examined the effect of pneumonitis on treatment efficacy and survival in the CJLSG1901 study, with a focus on differences in baseline patient characteristics. PATIENTS AND METHODS: Subgroup analyses were performed to explore the efficacy and safety of pembrolizumab plus pemetrexed in older patients with metastatic non-squamous NSCLC, focusing on whether pneumonitis developed after treatment initiation. RESULTS: Of the 48 patients included, five and four patients developed grade 1-2 and grade 3 pneumonitis, respectively. The pneumonitis group was predominantly male; postoperative recurrence was nearly twice as common in the group. Patients with pneumonitis received fewer treatment cycles. The objective response rates were 44.4% and 35.9% in the pneumonitis and non-pneumonitis groups, respectively. The median progression-free survival was shorter in the former. In contrast, the median overall survival was comparable between the groups. CONCLUSION: Although patients with pneumonitis had numerically higher response rates, their survival outcomes were comparable to those of patients without pneumonitis.