Exploring the applicability of immunotherapy in different EGFR mutation subgroups based on data analysis of 9,659 Chinese patients with NSCLC.

Abstract

e21020 Background: Here we assessed TMB level, PD-L1 expression, and their correlation in 9649 Chinese NSCLC patients with or without EGFR mutation, and different subtypes of EGFR mutations, to find out the underlying mechanisms that different outcomes of ICI for EGFR wild type and EGFR mutation NSCLC patients, and the possibility of ICI therapy for NSCLC patients of different EGFR mutation subtypes. Methods: Tumor tissue samples of 9649 NSCLC patients were collected from Janary 2018, expression of PD-L1 were detected by using Dako PD-L1 IHC 22C3 pharmDx, Tumor Proportion Score (TPS) was used to determine expression of PD-L1. Gene mutation was detected by means of next generation sequencing (NGS). Performed Whole-Exome Sequencing (WES) on 70 tissue samples and corresponding White Blood Cells (WBCs) as matched control. Other samples were detected with panel covering whole exon regions of 733 cancer related genes. All these detections were performed in a College of American Pathologists (CAP)-certified and Clinical Laboratory Improvement Amendments (CLIA)-accredited lab for gene mutation analysis (3D Medicines Inc.,Shanghai, China). Statistical analysis was performed using GraphPad Prism (version 7.01) and SPSS version 21.0 (SPSS,Inc.). Results: Results showed that the proportion of EGFR mutation in Chinese patients with NSCLC was 51.3%, and the proportion of EGFR mutation subtypes were 42.6% L858R, 39.5% exon 19del, 2.3% exon 20in, 4.3% T790M. These samples were divided into different groups according to EGFR mutation, both WES based and panel-based results showed that EGFR wild type group displayed higher TMB level than EGFR mutation group (P < 0.05). However, except for exon 19del, L858R, exon 20in, no significant differences were found between wild type and other EGFR mutation subtypes. Furthermore, results of IHC revealed that, higher proportion of strong positive PD-L1 expression (TPS≥50) were found in EGFR wild type than exon 19del, L858R and exon 20in, no significant correlation was found between TMB level and PD-L1 expression. Conclusions: EGFR mutations account for half of Chinese NSCLC patients. The biomarkers of immune checkpoint inhibitors (such as TMB and PD-L1) are different in various EGFR mutation subtypes, which may indicate that for some NSCLC patients with EGFR mutation subtypes, they may also respond to ICI treatment as wild-type.