Use of cyclin-dependent kinase 4/6 (CDK4/6) inhibitors in older patients with ER-positive HER2-negative breast cancer: Young International Society of Geriatric Oncology review paper

The current standard of care for the management of estrogen receptor (ER)-positive and human epidermal growth factor receptor 2 (HER2)-negative breast cancer has been redefined by the introduction of cyclin-dependent kinase 4/6 (CDK4/6) inhibitors. Although adults aged 65 years and older account for the majority of patients with breast cancer, limited data are available about the age-specific dosing, tolerability, and benefit of CDK4/6 inhibitors in this growing population. Older adults are under-represented in clinical trials and as a result, clinicians are forced to extrapolate from findings in younger and healthier patients when making treatment decisions for older patients. In this article, we review the limited age-specific evidence on the efficacy, toxicity, and quality of life (QoL) outcomes associated with the use of CDK4/6 inhibitors in older adults. We also describe ongoing trials evaluating CDK4/6 inhibitors in the older population and highlight that only a minority of adjuvant and metastatic trials of CDK4/6 inhibitors in the general breast cancer population includes geriatric assessments. Finally, we propose potential strategies to help guide decision making for fit and unfit older patients based on disease endocrine sensitivity, the need for rapid response and geriatric assessment.