Nab-paclitaxel (Abraxane) With or Without Mifepristone in Patients With Advanced Breast Cancer

This trial will find the best dose of mifepristone when given together with nab-paclitaxel (Abraxane) based on the side effects of the two drugs in patients with advanced breast cancer. Patients will be randomized to receive nab-paclitaxel with or without mifepristone during the first treatment cycle. After the first cycle, all patients will receive nab-paclitaxel with mifepristone until their disease worsens or they experience an unacceptable side effect. This study will test up to 4 doses of mifepristone in combination with nab-paclitaxel. The study will first test the lowest dose in a small group of patients and if they do not have bad side effects, higher doses will be tested.