Breast Cancer Coverage from Every Angle

Overall Survival With CDK4/6 Inhibitor in Hormone Receptor–Positive Breast Cancer

By: Lauren Harrison, MS
Posted: Wednesday, July 10, 2019

Patients with hormone receptor–positive, HER2-negative breast cancer experienced longer overall survival when treated with a cyclin-dependent kinase 4 and 6 (CDK 4/6) inhibitor, ribociclib, plus endocrine therapy compared with endocrine therapy alone. Sara Hurvitz, MD, of the University of California Los Angeles, and colleagues published their phase III trial results in The New England Journal of Medicine.

“This trial was unique because it looks at younger women who haven’t gone through menopause,” said Dr. Hurvitz in an institutional press release. “This is an important group to study since advanced breast cancer is the leading cause of cancer death in women 20 to 59, and the vast majority of breast cancer is hormone receptor–positive.”

Patients were randomly assigned to receive either ribociclib or placebo in addition to an endocrine therapy (goserelin and tamoxifen or a nonsteroidal aromatase inhibitor). The intention-to-treat population included 672 patients younger than age 59 with advanced hormone receptor–positive, HER2-negative breast cancer. Among the 335 patients in the ribociclib group, there were 83 deaths (24.8%), compared with 109 deaths among the 337 patients in the placebo group (32.3%).

Patients assigned to the combination therapy had a progression-free survival of 23.8 months, compared with 13 months for those taking the placebo. Overall survival after 42 months was 70.2% in the ribociclib group and 46% in the placebo group (hazard ratio = 0.71). A subgroup of patients receiving an aromatase inhibitor also saw the same survival benefit when taking ribociclib (hazard ratio = 0.70). Additionally, patients in the ribociclib group saw a longer time to disease progression during second-line therapy or to death compared with the placebo group (hazard ratio = 0.69). This study did not raise any new concerns regarding toxicity with ribociclib.

Disclosure: The study authors’ disclosure information may be found at

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