The Breast : official journal of the European Society of Mastology
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Palbociclib is a selective cyclin-dependent kinase (CDK) 4/6 inhibitor approved for use in postmenopausal women with hormone receptor-positive, human epidermal growth factor 2-negative (HR+/HER2-) advanced/metastatic breast cancer (ABC/MBC). Palbociclib has proven benefits in phase III placebo-controlled studies; however, real-world outcome data are lacking. The Ibrance Real World Insights (IRIS) study evaluated palbociclib use in patients with HR+/HER2- ABC/MBC in the real-world setting in the US, Argentina, and Germany. Here we describe results for the US patient subgroup. ⋯ In this first real-world assessment of clinical outcomes in US patients with HR+/HER- ABC/MBC, treatment with palbociclib in combination with AI or fulvestrant demonstrated favorable effectiveness in terms of progression-free and survival rates. Ongoing studies are needed to deliver mature clinical outcome data beyond 12/24 months in the real-world setting.
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Metastatic or advanced breast cancer (mBC/ABC) remains incurable despite many different systemic treatment options. Hormone receptor positive (HR+) disease represents the most common subtype in both early and advanced disease. A better understanding of the biology of this BC subtype, in particular regarding potential mechanisms of endocrine resistance, has led to the development of CDK4/6 inhibitors. ⋯ Overall survival (OS) has been reported so far only in 2 out of 7 trials as first line therapy and the difference did not reach statistical significance. In this article we review the biology of CDK signaling pathway and its inhibitors, preclinical and clinical data of all three investigated selective CDK4/6 inhibitors and their toxicity. We also discuss how these agents are being included in current international guidelines and future directions for these agents in other subtypes of breast cancer, in both advanced disease and early-stage disease.