The international, randomized phase III MONALEESA-7 trial found that adding ribociclib to standard-of-care endocrine therapy significantly improved overall survival for premenopausal women with advanced HR-positive/HER2-negative breast cancer compared with endocrine therapy alone.

After 42 months of follow-up, the survival rate was 70% for women who took the combination therapy compared with 46% for women who received endocrine therapy only. Advanced breast cancer is the leading cause of cancer death in women 20 to 59 years of age.

The study was featured in a press briefing on 4th June and presented at the 2019 American Society of Clinical Oncology (ASCO) Annual Meeting.

“This is the first study to show improved survival for any targeted therapy when used with endocrine therapy as a first-line treatment for advanced breast cancer,” said lead study author Sara A. Hurvitz, MD, Director of the Breast Cancer Clinical Research Program at UCLA Jonsson Comprehensive Cancer Center in Los Angeles, CA. “The use of ribociclib as a front-line therapy significantly prolonged overall survival, which is good news for women with this terrible disease.”

Advanced breast cancer is less common in premenopausal women than in older women, and incidence is increasing. In the United States, in women ages 20 to 39, the incidence of advanced breast cancer increased 2% per year between 1978 and 2008.

Ribociclib is a therapy that inhibits the activity of cancer-cell promoting enzymes known as cyclin-dependent 4/6 kinases (CDK 4/6). In July 2018, the U.S. Food and Drug Administration approved the expanded indication for ribociclib in combination with an aromatase inhibitor to include pre- and perimenopausal women with hormone receptor–positive, HER2-negative advanced or metastatic breast cancer.

About the Study
MONALEESA-7 is the first trial to focus exclusively on women under age 59 who were premenopausal and had advanced breast cancer for which they had not received prior endocrine therapy.

Investigators randomly assigned women to ribociclib (a tablet), or to a placebo tablet. All women also received goserelin, an injectable endocrine therapy that suppresses estrogen, and one of three other therapies: the nonsteroidal aromatase inhibitors letrozole (Femara) or anastrozole (Arimidex), which lower estrogen production, or tamoxifen, which has been used to treat breast cancer for over 40 years and blocks the effects of estrogen in breast tissue.

Six hundred and seventy-two women were enrolled in the study. After a median follow-up of 34.6 months, 173 (26%) were still receiving the therapies, with 116 (35%) of the women still receiving ribociclib and 57 (17%) still receiving the placebo. 

Next Steps
The researchers are doing analyses of patient-reported outcomes as well as sub-analyses of the clinical findings, including looking at biomarkers and circulating tumor DNA that may help them determine which women might benefit most from ribociclib.

The investigators are studying the use of ribociclib in women and men with early-stage HR+, HER2-negative breast cancer in combination with endocrine therapy and other cancer indications.

This study received funding from Novartis.

This article is a news release from 2019 ASCO Annual Meeting. Read the original here.