An Overview of the Roles of CDK4/6 Inhibitors in Metastatic Breast Cancer Elderly Patients.

Breast cancer is the most common type of cancer in women worldwide. Many studies indicate that breast cancer increases in elderly patients (≥70 years) and suggest that the higher cancer mortality in this population relative to that observed in younger women could be related to organ dysfunction, an advanced and delayed diagnosis, and other morbidities. Endocrine therapy (ET) represents the favorite treatment for patients affected by hormone receptor positive (HR+) metastatic breast cancer (MBC). Unfortunately, half of these patients are resistant to ET. In recent years, new therapeutic options, such as orally highly selective inhibitors of cyclin-dependent kinase 4 and 6 (CDK4/6), have been widely investigated in patients suffering from MBC with good outcomes. They are able to bypass resistance from hormonal therapy, by restoring hormone sensitivity and by delaying chemotherapeutic agent use. Thus, CDK4/6 inhibitors, combined with hormonal therapy, represent an alternative treatment for MBC. Unfortunately, the elderly population with MBC remains mostly excluded from clinical trials. Moreover, few data on the efficacy, safety, and short and longterm outcomes of therapies based on the combined treatment of ET and CDK4/6 inhibitors are available. This narrative review highlights the use of CDK 4/6 inhibitor-based therapy for MBC in elderly patients and suggests new therapeutic perspectives.