Expression of PD-L1 in Locally Advanced Breast Cancer and Its Impact on Neoadjuvant Chemotherapy Response.

Objectives: Programmed cell death-ligand 1 (PD-L1) is a new target in breast cancer (BC) and its impact on neoadjuvant chemotherapy (NACTH) response is still unclear. The aim of this study was to investigate the prevalence of PD-L1 in locally advanced invasive BC of different molecular subtypes and to elucidate its relation to tumor-infiltrating lymphocytes (TILs) density, established clinicopathological factors, pathological therapy response after neoadjuvant chemotherapy and patients' outcome.

Materials And Methods: One hundred and five cases of locally advanced invasive BC were enrolled in our study. Cases were classified into five molecular subtypes according to the Immuno-histochemical data. PD-L1 immunostaining was analyzed for all studied cases and its expression was correlated with TILs density, histopathologic parameters, BC molecular subtypes, Pathological therapy response, 7-years disease-free survival (DFS) and overall survival (OS).

Results: PD-L1 was expressed in 32.4% of the studied locally advanced BC cases. It showed a significant correlation with old age group (p= 0.010), high tumor grade (p= 0.046) and high pretherapy TILs density (p= <0.001). PD-L1 expression was higher in HER2/neu-enriched group (45.5%) followed by TNBC (44.4%). There were no significant relations between PD-L1 expression and DFS, OS as well as pathological therapy response, although, it revealed more expression in cases with complete and marked therapy response.

Conclusion: In spite our results fail to prove that PD-L1 is a bad prognostic biomarker in locally advanced BC, but they indicate PD-L1 could be a new target for the treatment of patients with high grade breast carcinoma and TNBC group.