Paricalcitol and Chemotherapy in Treating Women With Metastatic Breast Cancer

OBJECTIVES: Primary * To determine the ability to administer 8 continuous weeks of therapy within the first 3 months of enrollment with paricalcitol when given together with taxane or ixabepilone therapy in women with metastatic breast cancer. * To estimate the proportion of patients who successfully complete 8 continuous weeks of therapy as well as the proportion of patients who achieve a 'steady-state' dose. Secondary * To determine a dose of paricalcitol that can be taken continuously that maintains a normal calcium level when combined with a taxane or ixabepilone. * To determine if baseline levels of 25-hydroxycholecalciferol and parathyroid hormone (PTH) are associated with time to treatment failure in these patients. * To determine if PTH levels decline from baseline in patients treated with paricalcitol in combination with taxane or ixabepilone therapy. OUTLINE: Beginning on day 1, patients receive oral paricalcitol. The dose of paricalcitol is increased every 2 weeks until the serum calcium level is between 9 mg/dL and 11.4 mg/dL. Once this level is reached, the patient continues at that dose for the duration of the study. Patients also receive paclitaxel albumin-stabilized nanoparticle formulation, docetaxel, or paclitaxel once a week or once every 3 weeks or ixabepilone once every 3 weeks. Treatment continues for at least 12 weeks in the absence of disease progression or unacceptable toxicity.