MONALEESA-3 Study Findings Lead to Expanded FDA Approval of Ribociclib

A study published in the Journal of Clinical Oncology found that combining ribociclib and fulvestrant improved progression-free survival in postmenopausal women with hormone receptor-positive, HER2-negative metastatic or locally advanced breast cancer. The recently expanded FDA approval makes this combination available to this group of women.

Background

Fulvestrant (Faslodex) is a medicine used to stop the effect of estrogen that stimulates some cancer cells to grow. It is used to treat some hormone receptor-positive breast cancer. Ribociclib (Kisqali) is a type of targeted therapy called a CDK4/6 inhibitor. CDK4/6 inhibitors target two enzymes, called CDK4 and CDK6. that are important in cell division. CDK4/6 inhibitors interrupt the growth of cancer cells.

The researchers behind the phase III MONALEESA-3 study wanted to see if the combined use of these treatments lengthened the time from the start of treatment until the cancer grows or spreads, called progression-free survival, in postmenopausal women with advanced or metastatic hormone receptor-positive, HER2-negative breast cancer.

Design

The women participating in the study had never had treatment, had the cancer recur after hormonal therapy for early-stage breast cancer, or had one line of hormonal therapy for metastatic disease.

The trial randomly assigned the women to one of two treatment arms:

• 484 were assigned ribociclib (the treatment under study) plus fulvestrant
• 242 were assigned placebo (an inactive treatment) plus fulvestrant

Results

The researchers found that progression-free survival significantly improved in the women who received ribociclib plus fulvestrant, compared to the women given placebo plus fulvestrant.

Median progression-free survival rates were:

• 20.5 months for women taking the combination of ribociclib and fulvestrant
• 12.8 months for women taking the placebo and fulvestrant

Side effects of the combination treatment were similar to those expected from ribociclib or fulvestrant given alone. These may include:

• Fatigue
• Diarrhea
• Hair Loss
• Vomiting
• Constipation
• Headache
• Back pain

So far, participants have not been followed by the study long enough to know if one group lives longer than the other.

What This Means For You

This combination of ribociclib and fulvestrant could provide a new treatment option for postmenopausal women with advanced or metastatic HR-positive, HER2-negative breast cancer.

This was the first study to look at the use of a CDK4/6 inhibitor plus fulvestrant, and its results show potential for this new combined therapy and its safety and success.

At the 2018 ASCO Annual Meeting, Dennis J. Slamon, MD, PhD, director of Clinical/Translational Research at the UCLA’s Women’s Cancer Research Program, told OncLive.com the findings of MONALEESA-3 are exciting, and discussed the uniqueness of the trial group. Watch OncLive’s interview with Dr. Slamon here. 

In response to the findings, the FDA in July 2018 expanded the approval of ribociclib to include combining it with fulvestrant to treat postmenopausal women with HR-positive, HER2-negative advanced or metastatic breast cancer.

Slamon, D., Neven, P., Chia, S., et.al. Phase III Randomized Study of Ribociclib and Fulvestrant in Hormone Receptor–Positive, Human Epidermal Growth Factor Receptor 2–Negative Advanced Breast Cancer: MONALEESA-3. Journal of Clinical Oncology. 36, no. 24 (August 20 2018) 2465-2472.