Potential prognostic value of PD-L1 and FOXP3 as predictors of relapse in breast cancer

Background: Expression of PD-L1 detected by immunohistochemistry can represent a new hope for cancer management. The role of PD L1 in breast cancer is still unclear. Similarly, is the role of tumor-infiltrating FOXP3 +ve regulatory T (Treg) cells where literature data are conflicting. Our study aimed to evaluate the immunohistochemical expression of PD L1 and FOXP3 in breast cancer, correlate them with clinicopathological parameters as well as evaluating their relation.Methods: This is a retrospective study carried out on 136 breast cancer specimens. Only cases with proved pathological diagnosis of infiltrating duct carcinoma of no special type (NST) were included. Tissue microarray blocks were constructed and immunostained with the polyclonal antibody for PDL1 and monoclonal antibody for FOXP3.Results: Statistically significant correlation was found between high FOXP3 and nearly all adverse prognostic factors including; grade III tumors (p = .003), basal-like subtype(p = .001), high Ki67(p = .001), negative ER status(p = .001), negative PR(p = .028), HER2 expression(p = .04), advanced stage (p = .001), and LN metastases(p = .001). For PDL1, only statistically significant correlation with high Ki67 (p = .018) and advanced stage(p = .03) was found. A statistically significant positive correlation was found between PD L1 and FOXP3(p= .001). No statistically significant correlation was found between both PDL1 and FOXP3 in relation to disease-free survival (DFS) (p = .054). PDL1, age (≥ 50 years), nodal metastases were significant predictors of relapse in breast cancer.Conclusion: The current study supports PDL1 as a predictor of relapse in breast cancer. Additionally, it highlights the synergistic role between PDL1 and FOXP3 in breast cancer microenvironment. Each can be considered as a poor prognostic marker in breast cancer. This raises a concern about the benefit of breast cancer patients from blocking of PDL1 pathway.