Results from the phase III MONALEESA-2 trial showed a significant overall survival benefit with ribociclib plus endocrine therapy for postmenopausal patients with hormone receptor (HR)-positive, HER2-negative metastatic breast cancer. This is the first demonstration of a survival advantage with a front-line CDK4/6 inhibitor in postmenopausal patients with HR-positive/HER2-negative advanced breast cancer. Results were presented by Gabriel Hortobagyi, MD, and colleagues at the European Society for Medical Oncology (ESMO) Congress 2021 (Abstract LBA17_PR).
The randomized phase III trial showed a survival advantage of 63.9 months with front-line ribociclib and the aromatase inhibitor letrozole, compared to 51.4 months with hormone therapy alone. The estimated 6-year survival rate was 44.2% with ribociclib compared with 32% for placebo.
“These findings build on previous MONALEESA trials that achieved a survival benefit with the addition of ribociclib,” said Dr. Hortobagyi, Professor of Breast Medical Oncology at The University of Texas MD Anderson Cancer Center. “I am very encouraged that [patients with] metastatic breast cancer may have a treatment option that extends survival, delays chemotherapy treatment, and preserves their quality of life.”
Gabriel Hortobagyi, MD
Previously reported research showed that ribociclib and letrozole improved progression-free survival in postmenopausal women with HR-positive metastatic breast cancer in the MONALEESA-2 trial, while the combination resulted in an improved progression-free and overall survival benefit in premenopausal patients with advanced HR-positive breast cancer, according to results of the MONALEESA-7 trial.
MONALEESA-2, an international, double-blind study, enrolled 668 postmenopausal women with advanced breast cancer at 223 trial sites in 29 countries. They were randomly assigned to receive either ribociclib and letrozole or letrozole and placebo. None had been previously treated for their advanced disease. Trial participants were 82.2% White, 7.6% Asian, 2.5% Black, and 7.6% other.
The median follow-up was 79.7 months, and the time to first chemotherapy treatment was 50.6 months for patients who received ribociclib, compared to 38.9 months for placebo.
No new safety signals were observed, and adverse events were consistent with earlier reported phase III MONALEESA trial results.
“Given these results, the combination of a CDK4/6 inhibitor plus an aromatase inhibitor should be the standard first-line treatment for the majority of patients with advanced HR-positive breast cancer,” said Dr. Hortobagyi. “These findings have the potential to impact most women diagnosed with metastatic breast cancer.”
Disclosure: For full disclosures of the study authors, visit oncologypro.esmo.org.
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