目前，免疫检查点抑制剂（ICI）单药治疗已被批准用于具有PD-L1表达≥50％的晚期非小细胞肺癌（NSCLC）患者的治疗。然而，对于PD-L1表达<50％的患者，ICI单药治疗的疗效尚未完全阐明。本研究旨在确定PD-L1表达<50％的NSCLC患者中对单药免疫检查点抑制剂产生反应的临床特征和预测反应的因素。 回顾性分析了2012年7月至2022年12月期间接受ICI新药单药治疗的PD-L1肿瘤比例分数（TPS）≤50％的晚期或复发性NSCLC患者。在治疗后的反应评估中，将出现反应的患者与未出现反应的患者进行了比较。 在37名患者中，6名（16.2％）反应组的NSCLC患者对ICI单药治疗产生反应，并具有明显较低的体重指数（BMI）（p = 0.003）。与非反应组相比，反应组患者发生免疫相关不良事件（irAEs）的比例显著更高（p < 0.001）。多变量分析确定高BMI是预测PD-L1 <50％的NSCLC患者对ICI单药治疗无反应的显著独立危险因素。 在PD-L1 <50％的NSCLC患者中，BMI较高的患者更可能对ICI单药治疗无反应。此外，对ICI单药治疗产生反应的患者可能更容易发生irAEs，因此建议进行谨慎的随访。 © 2023 The Authors. Thoracic Cancer由中国肺癌专业组和John Wiley＆Sons Australia, Ltd.出版。

Immune checkpoint inhibitor (ICI) monotherapy is currently approved for the treatment of advanced non-small cell lung cancer (NSCLC) patients with programmed death ligand-1 (PD-L1) expression ≥50%. However, the efficacy of ICI monotherapy in patients with PD-L1 expression <50% has not yet been fully elucidated. The aim of this study was to identify the clinical characteristics of NSCLC patients with PD-L1 expression <50% who respond to single-agent ICIs and factors that predict response.Patients with advanced or recurrent NSCLC with a PD-L1 tumor proportion score (TPS) of 50% or less who received new monotherapy with an ICI between July 2012 and December 2022 were retrospectively analyzed. Patients with response were compared with those without response in the post-treatment response assessment.Among the 37 patients, six (16.2%) NSCLC patients in the response group responded to ICI monotherapy and had a significantly lower body mass index (BMI) (p = 0.003). Significantly more patients in the response group developed immune-related adverse events (irAEs) than in the nonresponse group (p < 0.001). Multivariate analysis identified high BMI as a significant independent risk factor predicting nonresponse to ICI monotherapy in NSCLC patients with PD-L1 < 50%.Among NSCLC patients with PD-L1 < 50%, those with a higher BMI were more likely to be nonresponders to ICI monotherapy. In addition, the group that responded to ICI monotherapy may have been at higher risk of developing irAEs, suggesting that careful follow-up is warranted.© 2023 The Authors. Thoracic Cancer published by China Lung Oncology Group and John Wiley & Sons Australia, Ltd.