Cabergoline in Metastatic Breast Cancer

Prolactin is a hormone produced in the pituitary gland. Previous studies have revealed that elevated levels of the hormone prolactin might be associated with an increased risk of breast cancer. Cabergoline has been shown to lower prolactin levels in the blood. The purpose of this study is to evaluate the effectiveness of cabergoline in treating metastatic breast cancer disease in those who test positive for the prolactin receptor.

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.