Phase II study of the progesterone antagonist mifepristone in patients with untreated metastatic breast carcinoma: a National Cancer Institute of Canada Clinical Trials Group study.

Mifepristone had minimal activity in this optimal group of patients. While there may be reason to conduct some clinical studies with it in combination with antiestrogens on the basis of some preclinical work, our data do not support its use as a single agent in the management of breast cancer.