Association between metastatic sites and first-line pembrolizumab treatment outcome for advanced non-small cell lung cancer with high PD-L1 expression: a retrospective multicenter cohort study

Associations between treatment outcomes of immune checkpoint inhibitors and metastatic sites in advanced non-small cell lung cancer (NSCLC) are not well known. Therefore, this multicenter retrospective study aimed to investigate the predictive factors of metastatic sites after first-line pembrolizumab treatment for advanced NSCLC with a PD-L1 tumor proportion score (TPS) >= 50%. We retrospectively analyzed advanced NSCLC patients with a PD-L1 TPS >= 50% who underwent first-line pembrolizumab therapy at 11 institutions between February 2017 and April 2018. Clinical data collected from medical records included metastatic sites at the time of pembrolizumab treatment. Treatment outcomes of pembrolizumab were assessed according to the Response Evaluation Criteria in Solid Tumors, version 1.1. In total, 213 patients were included in the study. The median age was 71 years (range 39-91 years). Of the 213 patients, 176 (83%) were men and 172 (81%) had an Eastern Cooperative Oncology Group performance status (ECOG-PS) score of 0-1. The most common metastases were thoracic lymph node metastasis (77%), intrapulmonary metastasis (31%), bone metastasis (28%), and malignant pleural effusion (26%). On multivariate analysis, a poor ECOG-PS score (hazard ratio: 1.95, 95.0% confidence interval: 1.25-3.04; P = 0.003) and malignant pleural effusion (hazard ratio: 1.52, 95.0% confidence interval: 1.01-2.29; P = 0.043) were independent predictors of shorter progression-free survival in patients treated with pembrolizumab. For NSCLC patients with malignant pleural effusion, pembrolizumab monotherapy is not a suitable first-line treatment because of its insufficient effectiveness, even though their PD-L1 TPS was high.