P37.10 PD-L1 Expression in Lymphovascular Tumor Emboli in Lung Adenocarcinoma

Abstract

PD-L1 expression by immunohistochemistry is the most widely used predictive biomarker of response to immune checkpoint inhibitors. Compared with PD-L1 expression in tumor tissue, the characteristics of PD-L1 expression in circulating tumor cells (CTCs) are less well understood. A major obstacle to study PD-L1 expression in CTCs is the lack of standardized method for PD-L1 expression detection in CTCs. All of the USFDA-approved standard PD-L1 assays are intended to use in tissue sections only, and not applicable to CTCs isolated from peripheral blood.