P2.04-47 Tumor Mutational Load, CD8+ T Cells, Expression of PD-L1 and HLA Class I to Guide Immunotherapy Decisions

Abstract

A minority of NSCLC patients benefit from anti-PD1 immune checkpoint inhibitor therapy. A rational combination of biomarkers is needed. The value of using a series of mechanism-of-action based parameters was studied for response prediction of immunotherapy: tumor mutational load (TML), CD8+ T cell infiltration, HLA class I expression and the currently used PD-L1 tumor proportion score. Patients were prospectively included between April 2016 and August 2017, and retrospectively analyzed. Metastatic NSCLC patients (n=30) with sufficient archival tissue, obtained prior to the first nivolumab administration, were selected. Response was assessed by RECIST v1.1. Progression-free survival (PFS) and overall survival (OS) were analyzed by Kaplan-Meier methodology. TML was determined using a next-genome sequencing panel (409 cancer-related genes). Immunohistochemistry was performed to score PD-L1, total CD8+ T cell infiltration and HLA class I. In 30 patients with adenocarcinoma (67%) or squamous cell carcinoma (33%), high TML was significantly associated with better PFS (p=0.004) and OS (p=0.025). Interaction analyses revealed that patients with both high TML and high total CD8+ T cell infiltrate (p=0.023) or no loss of HLA class I (p=0.026), patients with high total CD8+ T cell infiltrate and no loss of HLA class I (p=0.041) or patients with both high PD-L1 and high TML (p=0.003) or no loss of HLA class I (p=0.032) were significantly associated with better PFS. Unsupervised cluster analysis based on the four markers revealed three sub-clusters, of which cluster 1A was overrepresented by patients with progressive disease (15 out of 16), with significant effect on PFS (p=0.007). This proof-of-concept study suggests that a combination of PD-L1 expression, TML, CD8+ T cell infiltration and HLA class I expression function as a better predictive biomarker for the response to anti-PD-1 immunotherapy and PFS. Consequently, refinement of this proposed set of biomarkers and validation in a larger set of patients is warranted.