Cyclin-dependent kinase (CDK) 4/6 inhibitors have shown great results in numerous clinical trials and have improved the clinical outcome for patients with
hormone-receptor-positive, human
epidermal growth factor receptor 2-negative advanced
breast cancer significantly. To date, three CDK4/6 inhibitors are approved by the US Food and Drug Administration (FDA):
palbociclib,
ribociclib and
abemaciclib; the first two compounds are aproved by the European Medicines Agency (EMA) as well. In combination with endocrine
therapy, all of them led to significantly improved progression-free survival compared with endocrine
therapy alone. The aim of this article is to give an overview of the efficacy data and to describe the CDK4/6 inhibitor-based treatment-associated adverse events, including hematological and nonhematological adverse events. In addition, it describes the corrrect approach to patient monitoring and adverse event mangement and summarizes the current recommendations for
dose reductions and dose interruptions regarding the key adverse events, such as
neutropenia,
diarrhea, QTc prolongation and hepatobiliary toxicity. Accurate patient monitoring and management of the side effects is crucial, as several clinical trials in early
breast cancer are in progress and may lead to an additional approval in the neo-/adjuvant setting.