The Answer

The Answer is D. ER+ metastatic breast cancer. 

Three CDK4/6 inhibitors are approved for treatment: palbociclib, abemaciclib, and ribociclib. They are all indicated in therapy for patients with ER+, HER2-negative metastatic breast cancer. 

When used in conjunction with hormonal therapy or as a monotherapy (abemaciclib), progression-free survival rates have doubled. CDK4/6 inhibitors are continuing to be tested through clinical trials in other forms of breast cancer and other cancer types but have not yet been approved by the U.S. Food and Drug Administration and indicated for the other types of breast cancer listed.   

For additional information and resources on this topic, visit ONS’s targeted therapy resources.