P2.01-59 PD-L1 Very High Expression Associated with Clinical Outcome of Pembrolizumab Monotherapy of Advanced NSCLC with PD-L1 TPS of 50% or Greater

Abstract

Programmed cell death ligand 1(PD-L1) pathway-targeted immunotherapy is emerging as a promising therapeutic strategy for non-small-cell lung cancer (NSCLC). Especially, pembrolizumab monotherapy is a standard-of-care regimen for first-line treatment of advanced NSCLC with PD-L1 tumor proportion score (TPS) of 50% or greater. However, progressive disease rate of pembolizumab monotherapy for first-line treatment is 20-30%, and therefore we still need biomarkers in this clinical setting. We analyzed data of 41 patients with NSCLC with PD-L1 TPS of 50% or greater treated in Japanese Red Cross Ise Hospital, between March 2017 and January 2019. All patients received pembrolizumab monotherapy. We collected data of patient characteristics, histology, performance status (PS), stage, metastatic sites, smoking history, driver mutation, PD-L1 expression, treatment line from medical records. Progression-free survival(PFS) of pembrolizumab and Overall survival(OS) was calculated using Kaplan-Meier method. We compared PFS according to PD-L1 expression using log rank test and Cox model was used to assess the effect of PD-L1 expression on PFS. Patients were stratified into 2 PD-L1 groups based on PD-L1 expression: medium-high expression (TPS 50-74%), and very high expression (TPS 75-100%). The median age was 74 years (range: 43-86) and 15% of patients were women. The metastatic sites were brain (17%), pleural effusion (27%), bone (39%), liver (7%). The 22% of patients previously treated with chemotherapy and 78% of patients was treatment-naive. Median PFS of all patients was 7.0 months (CI95%. 4.2-16 months) and, median OS of all patients was not reached, respectively. In log-lank test, sex, smoking history, brain metastasis, pleural effusion, driver mutation, and PD-L1 expression were associated with PFS. In multivariate analysis using Cox model, only PD-L1 very high expression was associated with good prognosis (HR: 0.37, CI95%: 0.14-1.00). Even in cohort of PD-L1 TPS of 50% or greater, PD-L1 very high expression was predictive marker of pembrolizumab monotherapy.