Clinical Impact of PD-L1 Expression for Survival in Curatively Resected Colon Cancer

Programmed death 1 (PD-1) and its ligand PD-L1 play a key dysfunction of T lymphocytes. The purpose of this study was to assess and compare the prognostic role of tumor- TILs and its relationship with PD-L1 expression in stage II and III colon cancer.

Immunohistochemisty was used to assess the densities of CD8⁺, CD4⁺, and FOXP3⁺ cells, and PD-L1 expression in intraepithelial tumor site from 58 stage II and III colon cancers. These were evaluated for association with histopathologic features and overall survival.

PD-L1-positive tumors contained a higher number of CD8⁺ TILs with statistical significance (p = 0.001). CD4⁺ TILs showed positive correlation with PD-L1 expression (p = 0.034). There were no associations between PD-L1 expression and FOXP3⁺ TILs. Microsatellite instability (MSI)-high status (p = 0.001; Odd ration 18.0; 95% CI = 4.3-74.8) was the strongest prognostic factor along with mucinous/poor cell differentiation, CD8 and right tumor location was associated with PD-L1 expression (p = 0.024, 0.035 and 0.033, respectively).

This study demonstrated that PD-L1 expression was associated with MSI-high, increased CD8⁺ TILs, mucinous and poor cell differentiation, and right-sided tumor location.