Comparing Molecular Biomarker Testing With Immunohistochemical Staining In Predicting Response To Neoadjuvant Therapy In Breast Cancer

Abstract Background: Breast cancer (BC) is the most common cancer type among women world-wide and the major cause of cancer deaths. Many factors affect the prognosis and treatment of BC such as histological grading, staging, as well as the biological markers: Estrogen receptor (ER), Progesterone receptor (PR), HER2 and Ki67. Immunohistochemistry (IHC) remains the corner stone in determining ER, PR, HER2 and Ki67 status for breast cancers, however limitations still exist concerning analytic validity & interpretation. mRNA expression assays can provide an alternative innovative method for measuring these biomarkers. The Xpert Breast Cancer STRAT4 Assay is an in vitro diagnostic test for the determination of overexpression or non-overexpression of ER, PR, HER2 and Ki67 mRNA isolated from 10% neutral buffered FFPE invasive breast tissue.Objectives: Comparing results (concordance) of IHC of ER, PR, Ki67 and Her2 with mRNA gene expression analysis results by STRAT4 for each of the biomarkers tested on the same sample blocks & correlating the results of IHC with the clinico-pathologic parameters of the tumours and clinical outcome of patients. Materials and methods: One hundred BC tissue sections were collected from needle biopsies specimens & were evaluated for expression of the four biomarkers (ER, PR, KI67, Her-2) using IHC and the same blocks were sectioned and tested for mRNA gene expression by the Xpert breast cancer STRAT4 for the same markers. Results: Concordance rate between mRNA expression and IHC was 96% for ER, 94.7% for PR, 93% for HER-2, 97.9% for Ki67, with Kappa measurement showing strong to perfect agreement in the 4 parameters (all > 80%).Conclusion: The study reveals high concordance between central IHC and mRNA measurements of the four main breast cancer biomarkers. STRAT4 can provide an effective modality for standardized results for breast cancer patients.