Programmed Death-Ligand 1 Tumor Proportion Score and Overall Survival From First-Line Pembrolizumab in Patients With Nonsquamous Versus Squamous NSCLC

Introduction: For patients with NSCLC receiving immune checkpoint inhibitors, programmed death-ligand 1 (PD L1) tumor proportion score (TPS) has been validated as a predictive biomarker for improved overall survival (OS). Nevertheless, its histology-specific predictive value in patients with advanced squamous versus nonsquamous cancers remains unclear. To evaluate the differential value of PD-L1 TPS as a predictive biomarker for OS after first-line pembrolizumab in patients with squamous versus nonsquamous NSCLC. Methods: Retrospective, observational study of patients diagnosed with having advanced NSCLC who were treated between October 2015 and April 2019 at community oncology clinics and academic medical centers in a deidentified electronic health record-derived database. Included patients were diagnosed with having advanced or metastatic NSCLC, received treatment with first-line, single agent pembrolizumab, and had documentation of PD-L1 testing with a numeric result. Exclusion criteria included alterations in EGFR, ALK, and ROS1. The primary end point was OS from start of first-line pembrolizumab therapy by squamous or nonsquamous histology and PD-1 expression level measured by TPS (low, <50% or high, >50%). Results: The cohort of 1460 patients with NSCLC who received pembrolizumab as a first-line therapy had a mean age of 72 years. Histology was 28% squamous and 72% nonsquamous. PD-L1 expression was low in 13% and high in 87%. No meaningful differences in age, sex, or smoking history were observed by PD-L1 TPS or histology type. A generalized gamma model adjusting for sex and stage at diagnosis found that for patients with nonsquamous his-tology, high PD-L1 TPS was significantly associated with improved OS by a median OS difference of 8.4 months (p < 0.001). In contrast, for patients with squamous histology, there was no evidence of association between PD-L1 expression level and OS (p = 0.283). PD-L1-related incre-mental differences in median OS between the patients with squamous and nonsquamous tumors were significantly different (p = 0.034). Conclusions: Among patients with NSCLC treated with first-line pembrolizumab, high PD-L1 TPS is associated with OS among patients with nonsquamous NSCLC, but not among patients with squamous NSCLC. (c) 2021 International Association for the Study of Lung Cancer. Published by Elsevier Inc. All rights reserved.