CDK 4/6 Inhibitor Ribociclib Improves Overall Survival for Premenopausal Women With Metastatic, Hormone Receptor-Positive Breast Cancer

The addition of the CDK 4/6 inhibitor ribociclib (Kisqali) to hormonal therapy as the first treatment for premenopausal women with metastatic, hormone-receptor positive breast cancer, resulted in women living longer than they would if given hormonal therapy alone. These updated results from the phase III MONALEESA-7 trial were presented at the 2019 ASCO Annual Meeting on Tuesday.

The MONALEESA-7 trial previously proved that adding ribociclib to hormonal therapy helped women go longer without breast cancer growing, called progression-free survival. Medicines for metastatic disease often get approval based on measures like progression-free survival. But overall survival, the length of time from the start of treatment until death, is the most important goal for trials of medicines because it helps show by how much the medicine might lengthen a person’s life. Overall survival is more difficult for clinical trials to show, and it often takes longer to find this effect.

The trial included 672 premenopausal women – women who still have regular periods – who were assigned to get either

• ribociclib, hormonal therapy, and goserelin (Zoladex), a medicine that suppresses the function of the ovaries, or
• a placebo, hormonal therapy, and goserelin

The results presented this week show that adding ribociclib to hormonal therapy resulted in a 29 percent reduction in the risk of death compared to hormonal therapy given with a placebo. Researchers found that 42 months after starting treatment

• 46.0 percent of women given placebo and hormonal therapy were still alive
• 70.2 percent of women given ribociclib and hormonal therapy were still alive

Researchers reported that 35 percent of women assigned to the ribociclib plus hormonal therapy group were still receiving that treatment at the time of this analysis.

Ribociclib and other CDK 4/6 inhibitors are FDA approved and part of standard care for metastatic, hormone-receptor positive breast cancer. The researchers for MONALEESA-7 note that this is the first time a CDK 4/6 inhibitor, given with hormonal therapy, has shown an overall survival benefit that is statistically significant, meaning it isn’t likely the result of chance. These findings strengthen the continued use of ribociclib and CDK 4/6 inhibitors in metastatic, hormone receptor-positive breast cancer.