Cabergoline in Metastatic Breast Cancer

Inclusion Criteria:

Patients must have histologically confirmed metastatic breast cancer; tissue (a minimum of 3 slides) from the most recent biopsy is required for review and confirmation of eligibility; NOTE: material should ideally be from the metastatic disease, however material from the primary tumor is acceptable if that is all that is available
Patients must have stage IV breast cancer
Patients must have tumors (primary or metastatic) that stain positively for the prolactin receptor

Patients may have measurable or evaluable disease

Measurable disease is defined as at least one lesion that can be accurately measured in at least one dimension (longest diameter to be recorded) as > 20 mm with conventional techniques or as > 10 mm with spiral CT scan
Evaluable disease is disease that does not meet the criteria for measurable disease; examples would include patients with effusions or bone-only disease
Women of childbearing potential must commit to the use of effective barrier (non-hormonal) contraception while on study
Patients must have a life expectancy of greater than 12 weeks
Patients must have an Eastern Cooperative Oncology Group (ECOG) performance status =< 2
Patients may have had a prior diagnosis of cancer if it has been > 5 years since their last treatment
Leukocytes >= 3,000/uL (microliter)
Absolute neutrophil count >= 1,500/uL
Platelets >= 100,000/uL
Child Pugh score =< 10
Patients must be able to swallow and retain oral medication
All patients must have given signed, informed consent prior to registration on study

Exclusion Criteria:

Women who are pregnant or lactating are not eligible for study treatment
Patients who are undergoing concomitant radiotherapy are NOT eligible for participation
Patients who are receiving any other investigational agents or concurrent anticancer therapy are NOT eligible for participation; previous systemic treatment is allowed with a 2 week washout period prior to registration
Patients who are taking any herbal (alternative) medicines are NOT eligible for participation; patients must be off any such medications by the time of registration
Patients who are receiving concomitant D2-antagonists (such as phenothiazines, butyrophenones, thioxanthenes, or metoclopramide) are NOT eligible for participation; patients must be off any such medications by the time of registration
Patients with known brain metastases are NOT eligible for participation

Patients with any of the following conditions or complications are NOT eligible for participation:

Uncontrolled hypertension
Known hypersensitivity to ergot derivatives
History of cardiac valvular disorders, as suggested by anatomical evidence of valvulopathy of any valve (to be determined by pre-treatment evaluation including echocardiographic demonstration of valve leaflet thickening, valve restriction, or mixed valve restriction-stenosis)
History of pulmonary, pericardial, cardiac valvular, or retroperitoneal fibrotic disorders
Gastrointestinal (GI) tract disease resulting in an inability to take oral medication
Malabsorption syndrome
Require intravenous (IV) alimentation
History of prior surgical procedures affecting absorption
Uncontrolled inflammatory GI disease (e.g., Crohn's, ulcerative colitis)