Advances in Molecular Diagnostics and Targeted Therapeutic Approaches in HER-2 Positive Breast Cancer

Human epidermal growth factor receptor 2 (HER2) is linked with aggressive tumors in breast carcinoma patients and results in poor outcomes. HER2 signaling in breast cancer also interacts with phosphoinositide-3-kinase (PI3K)/Akt signaling route, mitogen-activated protein kinase (MAPK) pathways, and protein kinase C (PKC) activation. Hence, the diagnosis of HER2-positive status and targeting of HER2 in breast cancers is of vital importance as it forms the basis for trastuzumab therapy. Immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) are the conventional methods that have been used for the diagnosis of HER2 status in breast cancer individuals. However, with the advancements in molecular diagnosis techniques like quantitative real-time reverse transcription-PCR (RT-qPCR) have been established with a series of evaluations to complement the diagnosis made through the conventional methods. The advances in molecular diagnosis have paved the way for precision medicine and targeted therapy in HER2-positive breast carcinoma.  Based on the HER2 status, the breast cancer patients may be administered with antibodies, antibodies drug conjugates (ADC) or tyrosine kinase inhibitors. Since a significant role of the immune microenvironment has been established, monoclonal antibodies and immunotherapy options are also being evaluated for the management of breast carcinoma. Various clinical trials have highlighted the role of targeted therapy in breast cancer individuals. We present a review on the advances in molecular diagnosis of HER2 status in breast cancer individuals along with the role of targeted therapy in the management of HER2-positive breast carcinoma.