Significance of immune checkpoint proteins in EGFR-mutant non-small cell lung cancer

Objectives: To characterize the expression of PD-L1, PD-1, cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and T-cell immunoglobulin and mucin-domain containing-3 (TIM3) in epidermal growth factor receptor (EGFR) mutant non-small cell lung cancer (NSCLC). Materials and methods: Samples from 90 patients with newly diagnosed advanced stage NSCLC harboring EGFR mutations and treated with first line EGFR tyrosine kinase inhibitors (TKI) within 3 months of diagnosis were stained for CTLA-4, PD-L1, PD-1, TIM-3 and CD3 expression by immunohistochemistry. Results: PD-L1 was present in at least 1% of immune and tumor cells in 44% and 59% of samples, respectively. In multivariate analysis, increased CD3 immune shaped cell (ISC) counts (HR 2.805, p = 0.034) and high PD-L1 tumor H-score (HR 3.805, p = 0.022) was associated with a shorter progression free survival and high CTLA-4 ISC counts was associated with borderline overall survival significance (HR 1.054, p = 0.061). Conclusion: Tumor PD-L1 expression was significantly associated with a shorter PFS whereas immune cell CTLA-4 may be prognostic for OS. Our findings support the ongoing development of CTLA-4 and PD1/PD-L1 inhibitors in this important molecularly defined subset of lung adenocarcinoma. (C) 2017 Elsevier B.V. All rights reserved.