EXPRESSION OF PROGRAMMED DEATH-LIGAND 1 PD-L1 IN HER2- NEU POSITIVE BREAST CANCER CORE BIOPSY

Abstract

Aims: Clinical research has demonstrated that the programmed death (PD)- 1-PD-ligand 1 (PD-L1) axis is a promising therapeutic target in variable malignancies. This route has recently received a lot of attention. We aim to identify the expression of PD-L1 in HER2-positive breast cancer cases using an immunohistochemical study and to investigate the association between the expression of PD-L1 and several clinicopathological parameters.

Material and methods: This is both a retrospective and prospective case study performed on 50 formalin-fixed paraffin-embedded tissues (core biopsy) in the North of Iraq over 7 months extending from November 2021 through May 2022.  The study evaluates PD-L1 protein immunohistochemical expression using PD-L1 IHC 22C3 pharmDx (Dako) monoclonal mouse Anti-PD-L1, clone 22C3, assessed and scored using a combined positive score, in which both tumor cells and tumor-infiltrating immune cells (TCIC) are used in relation to viable tumor cells and its correlation with various histopathological parameters.

Results: PD-L1 expression was correlated with high TILs levels (p<0.05), vascular invasion (p<0.05), and no significant correlation with the grade, age, side, and necrosis (p>0.05).

Conclusions: Our findings demonstrate that PD-L1 is expressed in a third of HER2 breast cancer, this may potentially be useful in therapy prediction for a patient who does not benefit from Trastuzumab treatment, PD-L1 expression correlated with LVI, and TIL.