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

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.

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).

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.

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.