PD-L1 Expression of Tumor Cells, Macrophages, and Immune Cells in Non–Small Cell Lung Cancer Patients with Malignant Pleural Effusion

Abstract Introduction Whether immunohistochemical staining of programmed death ligand 1 (PD-L1) on cells of pleural effusion could be used to predict response to immunotherapy treatment has not been reported. Methods We retrospectively enrolled patients who had undergone malignant pleural effusion drainage and had effusion cell block specimens from 2014 to 2016. Immunohistochemical staining for PD-L1 was performed with tumor cells, immune cells, and macrophages of all cell block specimens. Immunoactivity was scored as 0 for absence of staining and 1+ for faint, 2+ for moderate, and 3+ for intense membranous staining. Patients' clinicopathological characteristics were also collected. Results PD-L1 expression of pleural effusion tumor cells was associated with the PD-L1 expression of macrophages ( p  = 0.003) and immune cells ( p p  = 0.012), smoking status ( p  = 0.032), and Eastern Cooperative Oncology Group performance status ( p  = 0.017). The PD-L1 expression of immune cells was associated with the overall survival of patients ( p  = 0.004). Conclusions These results suggest that there might be an immune interaction between pleural effusion tumor cells and macrophages. The low intensity of PD-L1 expression in immune cells is associated with the poor survival of patients with lung cancer with malignant pleural effusion.