This study tests the hypothesis that SU11248 can delay tumor progression after tumor mass reduction by taxanes. This is a dual-arm open-label randomized multicenter phase II clinical trial with 2:1 randomization evaluating the efficacy of SU11248 versus nil in patients with metastatic breast cancer after objective response to taxane chemotherapy. Patients randomized to the placebo arm (Arm B) will be offered the opportunity to receive open-label SU011248 treatment upon development of Response Evaluation Criteria in Solid Tumors (RECIST)-defined disease progression.