For the first time, researchers have proven that a CDK4/6 inhibitor is effective in younger, pre- and perimenopausal women with advanced HR-positive/HER2-negative breast cancer. These patients often have few treatment options. But a new study presented at the 2017 San Antonio Breast Cancer Symposium, offers hope. Results of phase 3 of the MONALEESA-7 trial showed that adding ribociclib (Kisqali) to standard endocrine therapy with temporary ovarian suppression significantly improved progression-free survival (PFS) when used as a first-line treatment for this patient group.
The median PFS was 23.8 months for women who received ribociclib in combination with either tamoxifen or a nonsteroidal aromatase inhibitor (AI) and goserelin, a luteinizing hormone-releasing hormone analog, compared with 13.0 months for those who received the standard endocrine therapy plus placebo (hazard ratio [HR], 0.553; 95% CI, 0.441-0.694; P <.0001).1
For patients who received the regimen containing ribociclib and tamoxifen, the median PFS was 22.1 months compared with 11.0 months for the placebo arm (HR, 0.585; 95% CI, 0.387-0.884). Combining ribociclib with an AI resulted in 14-month improvement in median PFS compared with an AI alone (27.5 vs 13.8 months; HR, 0.569; 95% CI, 0.436-0.743).
The overall response rate was 51% versus 36% in favor of the experimental arm. Patient-reported outcomes showed that ribociclib was associated with a statistically significant improvement in time to deterioration, as well as a durable, clinically meaningful reduction in pain score as early as 8 weeks after initiation.
MONALEESA-7 is the first clinical trial to have the statistical power to show that ribociclib is associated with clinical benefit specifically for pre- and perimenopausal women with HR-positive/HER2-negative advanced breast cancer, and the first to show that the CDK4/6 inhibitor is effective in combination with either tamoxifen or a nonsteroidal AI together with ovarian suppression using goserelin, according to lead investigator Debu Tripathy, MD, who discussed the findings during a press briefing. Tripathy is a professor of medicine and chair of the Department of Breast Medical Oncology at The University of Texas MD Anderson Cancer Center.