Programmed Cell Death Ligand 1 and Venous Thromboembolism in Patients with Primary Brain Tumors

Background: Programmed cell death ligand 1 (PD-L1) is an immune suppressive molecule frequently expressed in high grade gliomas. Given the correlation of inflammatory processes and thromboembolic events in cancer patients, we aimed to investigate the association of PD-L1 expression in primary brain tumors with venous thromboembolism (VTE).

Methods: The study was conducted within the framework of the Vienna Cancer and Thrombosis Study (CATS). Patients with newly diagnosed primary brain tumors (> 90% glioma) or progression after remission were included and observed for a time period of two years. Primary endpoint of the study was symptomatic and objectively confirmed VTE. PD-L1 expression of brain tumor samples was assessed by immunohistochemical staining. The PD-L1 signal was scored based on the percentage of tumor cells presented with a specific membranous signal.

Results: In the current study, 20/206 (9.7%) brain tumor samples stained positive for membranous PD-L1 expression in ≥1% of tumor cells and 13/206 (6.3%) samples showed membranous PD-L1 expression in ≥5% of tumor cells. In total, 27/206 (13.1%) patients developed VTE. There was no association between increased tumor PD-L1 expression and the risk of VTE (≥5% PD-L1 versus < 5% PD-L1: 2/13 (2-year competing risk cumulative incidence of VTE: 15.4%) versus 25/193 (2-year cumulative incidence: 13.2%), Gray's test p=0.796).

Conclusion: Based on our results, PD-L1 expression in primary brain tumors is not associated with the risk to develop VTE.