CDK4 and CDK6 Inhibition in Breast Cancer — A New Standard

Breast cancer is the most prevalent type of malignant neoplasm worldwide, and estrogen-receptor (ER)–positive breast cancer is the most common phenotype. Outcomes continue to improve, but many patients present with advanced disease or have recurrence of disease that progressively becomes resistant to endocrine therapy. Efforts to enhance responsiveness to treatment and to overcome primary or acquired resistance through cotargeting of estrogen and cell proliferation–survival signaling pathways led to the recent approval of phosphatidylinositol 3-kinase–Akt–mammalian target of rapamycin (PI3K/Akt/mTOR) and cyclin-dependent kinase 4 and 6 (CDK4 and CDK6) inhibitors for the treatment of advanced ER-positive, human epidermal growth factor receptor 2 . . .