The combination of antiestrogen therapy and ribociclib, an investigational 
CDK4/6 inhibitor, led to improved outcomes in women with metastatic HR-positive, 
HER2-negative breast cancer, according to findings presented at a meeting of the 
European Society for Medical Oncology. The combination significantly increased 
progression-free survival compared with letrozole alone in a large phase III 
trial-data that could lead to FDA approval.