P2.01-064 Molecular Context of Immune Microenvironment in Early-Stage Lung Squamous Cell Carcinoma

Abstract

Although it has been proposed that the number of somatic mutations, together with high PD-L1 and CD8 expression, defines a type of tumor microenvironment predictive of response to immune checkpoint inhibitors, this data has been challenged because the methodologies are difficult to reproduce (e.g. tissue microarrays, whole exome sequencing or complicated scoring approaches). This situation prompted us to investigate possible alternatives that are easier to reconcile with daily practice. A total of 40 consecutive patients with early stage lung squamous cell carcinoma who underwent surgery at HM Sanchinarro University Hospital were considered. Automated immunohistochemistry (IHC) for PD-L1 expression was performed on whole tissue sections (Benchmark ULTRA, OptiView, Ventana Medical Systems, USA) with three different antibodies: SP142 (Ventana), SP263 (Ventana), and E1L3N (Cell Signaling). PD-L1 IHC was considered positive according to the criteria used in the corresponding clinical trials. P53 aberrant IHC expression was used as a surrogate marker for TP53 mutations. Whole tissue sections were also automatically scored for CD8+ tumor-infiltrating lymphocytes (TILs) density (off-label algorithm on the iScan Coreo). Afterwards, we performed targeted next-generation sequencing (NGS) in 52 genes (Oncomine Focus AssayTM, Life Technologies, USA). The prognostic impact of all these variables was also evaluated. Correlation between E1L3N and SP142 or SP263 was similar when scoring tumor cells (TCs) (0.94). There was a significant association between the intraepithelial and peritumor stromal CD8+ TILs density and overall survival when using the image analysis software (p=0.032). The presence of >247 CD8+ cells/mm2 had a 94% specificity and a 67% sensitivity for identifying patients with at least 5% SP142 PD-L1+ TCs. The highest percentage of PD-L1+ TCs were found in samples with CDK6 (2.6%) or MYC (2.6%) amplifications. Cases with FGFR1 amplification (7.9%) were negative for all PD-L1 antibodies. P53 aberrant expression and PD-L1 expression in TCs also seem to be related. The methodology presented herein could help align the use of targeted NGS and the immune microenvironment assessment to increase the clinical value of immune checkpoint inhibitors. Acknowledgements This study was partially funded by Instituto de Salud Carlos III (ISCIII), Fondo de Investigaciones Sanitarias (FIS), Fondos FEDER-Plan Estatal de I+D+I 2013-2016 (PI14-01176).