Breast cancer is the most common cancer in Canadian women. In 2007 an estimated 22,300 women will be diagnosed and 5300 will die of the disease. Despite advances in therapy, metastatic disease remains an incurable illness, with a median survival of only 2 years. Standard systemic treatment options for metastatic disease include chemotherapy or hormonal therapy. Radiation is frequently used in the metastatic setting for palliation of symptoms, with the most frequent site of radiation being bone. Response rates to first line chemotherapy are in the range of 30%, however these responses are not durable. Currently there are no curative options for metastatic disease, underscoring the need for novel therapeutic approaches.