Cabozantinib +/- Trastuzumab In Breast Cancer Patients w/ Brain Metastases

This research study is a Phase II clinical trial. Phase II clinical trials test the safety and effectiveness of an investigational intervention to learn whether the intervention works in treating a specific disease. "Investigational" means that the intervention is being studied. The FDA (the U.S. Food and Drug Administration) has not approved cabozantinib for your specific disease but it has been approved for other uses. Few treatments exist for brain metastases from breast cancer. Radiation and surgery are generally included as a possible standard of care treatments for this diagnosis. In this research study, the investigator are looking at how well cabozantinib works in treating breast cancer that has spread to the brain. Cabozantinib has been used in some phase I studies and information from those other research studies suggests that cabozantinib may help to shrink or stabilize the participant's breast cancer. In addition, information from these studies has shown that cabozantinib may pass through the blood brain barrier (a protective layer that prevents most large molecules and cells found in the blood from entering the brain tissue) and may be an effective treatment for brain metastases. If the participant has HER2-positive breast cancer, they will receive trastuzumab in addition to cabozantinib. Trastuzumab is an FDA approved drug for the treatment of HER2-positive metastatic breast cancer. However, the combination of cabozantinib and trastuzumab has not yet been tested. Trastuzumab may help to shrink or stabilize breast cancer in combination with cabozantinib. If the participant's breast cancer is HER2-negative, they will not receive trastuzumab as part of this clinical trial. The names of the study interventions involved in this study are: * Cabozantinib (XL184) * Trastuzumab (herceptin) (participants with HER2-positive disease only)