Optimizing care for younger women with hormone receptor-positive, HER2-negative metastatic breast cancer

Treatment strategies for hormone receptor-positive (HR⁺ ), human epidermal growth factor receptor 2-negative (HER2^- ) metastatic breast cancer in young women (<40 years at diagnosis) have traditionally been extrapolated from data obtained from trials conducted either exclusively or predominantly in the postmenopausal setting. These young patients are usually treated with ovarian function suppression (OFS) + endocrine therapy (ET) ± targeted therapy, except if there is a concern about endocrine resistance or a need to gain rapid disease control due to the onset of visceral crisis. This review examines evidence that supports the use of a cyclin-dependent kinase 4/6 inhibitor, in combination with OFS and ET, when treating premenopausal or perimenopausal women with HR⁺ /HER2^- metastatic breast cancer. This includes data from the MONALEESA-7 study (treating only premenopausal/perimenopausal women in the first-line setting), and the results of subgroup analyses from the PALOMA-3 and MONARCH-2 trials. We also consider a number of age-specific challenges that younger breast cancer patients can face, highlighting the importance of a multidisciplinary approach to ongoing care.