The Use of Cyclin-Dependent Tyrosine Kinase 4/6 (CDK4/6) Inhibitors in Breast Cancer

Abstract

Breast cancer has the highest prevalence of all cancers in females, with roughly 2.26 million new cases diagnosed and an estimated 0.68 million deaths/year. Hormone receptor-positive (HR+) or human epidermal growth factor receptor-negative (HER2-) illness affects the vast majority of patients with metastatic breast cancer (MBC). Endocrine therapy (ET) with aromatase inhibitors (AIs) is the preferred first-line choice for this subpopulation. However, because most patients developed tolerance to these medications, demand for alternate endocrine regimens has surged. Inhibition of cyclin-dependent kinase 4 and 6 (CDK4/6) is proving to be a success in resistant patients as well as a first-line treatment. This review article highlights the current indications for CDK4/6 inhibitors in breast cancer that have been approved by the FDA. The literature search was confined to the years 2015 to 2020, and 27 articles and 6 studies were chosen for further research from a large number of publications. In hormone receptor-positive, HR RC+, HER2- advanced or metastatic breast cancer (ABC/MBC) patients, the use of currently available CDK4/6 inhibitors, either alone (abemaciclib) or in combination with endocrine therapy (Palbociclib and Ribociclib), showed a beneficial effect when compared to endocrine therapy alone. The use of CDK4/6 inhibitors resulted in longer progression-free survival (PFS), greater clinical benefit rates (CBR), and an overall response rate (ORR), as well as an overall survival (OS) advantage in patients previously treated with endocrine treatment (ET).