Cabergoline in Metastatic Breast Cancer

PRIMARY OBJECTIVES: I. To evaluate overall response rate (ORR) of cabergoline in women with metastatic breast cancer. SECONDARY OBJECTIVES: I. Evaluate the progression-free survival (PFS) and overall survival (OS). II. Evaluate toxicity. III. Correlate serum prolactin levels during therapy with response. IV. Evaluate within-patient changes in computed tomography (CT) and bone scan measurements taken at baseline and after 2 cycles of treatment. V. Evaluate within-patient changes in prolactin receptor (PRLr) expression from baseline to after 1 cycle of treatment in those patients who consent to optional repeat biopsy. OUTLINE: Patients receive cabergoline orally (PO) twice weekly for weeks 1-4. Courses repeat every 4 weeks in the absence of disease progression or unacceptable toxicity. After completion of study treatment, patients are followed up at 30 days and then every 6 months thereafter.