The programmed death-1/programmed death-ligand 1 (PD-L1) pathway is a negative feedback pathway that suppresses the activity of T cells. Previous studies reported that high PD-L1 expression on tumor cells (TC) was associated with poor survival in patients with colorectal cancer; however, the prognostic evaluation of these studies was limited because they included patients at various disease stages. The purpose of the present study was to evaluate the relationship between PD-L1 status in the immune microenvironment and the clinicopathological features of stage III colorectal cancer. Two hundred and thirty-five patients were included in the analysis. PD-L1 expression on TC and tumor-infiltrating mononuclear cells (TIMC) was evaluated by immunohistochemistry. The median follow-up of thisi study was 52.9 months. A total of 8.1% of stage III colorectal cancer showed high PD-L1 expression on TC and 15.3% showed high PD-L1 expression on TIMC. Patients with high PD-L1 expression on TC had significantly shorter disease-free survival (DFS) than patients with low expression (hazard ratio [HR] 2.36; 95% confidence interval [CI], 1.21-4.62; P = 0.012). In addition, patients with high PD-L1 expression on TIMC were associated with longer DFS than patients with low expression (HR 0.40; 95% CI, 0.16-0.98; P = 0.046). These findings suggest that PD-L1 expression status may be a new predictor of recurrence for stage III colorectal cancer patients and highlight the necessity of evaluating PD-L1 expression on TC and TIMC separately in the tumor microenvironment.
Keywords: CD8-positive T-lymphocytes; colonic neoplasms; immune microenvironment; immunohistochemistry; tumor infiltrating mononuclear cells.
© 2017 The Authors. Cancer Science published by John Wiley & Sons Australia, Ltd on behalf of Japanese Cancer Association.