Focused Ultrasound and Pembrolizumab in Metastatic Breast Cancer

Inclusion Criteria (summary): * Histologically confirmed metastatic or unresectable breast cancer * Any receptor status (estrogen receptor, progesterone receptor, HER2 receptor). Patients who are HR+ should also no longer be candidates for hormonal-based therapy. Patients who are HER2+ should have progressed on or no longer be candidates for available HER2 directed therapy. Hormonal therapy must be stopped prior to day 1 of treatment. * Patients must have had at least one prior line of therapy for breast cancer in the metastatic setting. * Patients must have an accessible lesion in the breast/chest wall/axilla which has not been previously thermally ablated. Prior breast irradiation is acceptable if the lesion has recurred or grown following radiation. * Patients must agree to use an adequate method of contraception for the course of the study through 120 days after the last dose of study medication. * Patients must have at least one target lesion in breast/chest wall/axilla which is amenable to application of high intensity focused ultrasound: * Patients must be willing to provide tissue from a newly obtained core or excisional biopsy of a tumor lesion. * Performance status of 0 or 1 on the ECOG Performance Scale. * Adequate organ function Exclusion Criteria (summary): * Patients currently participating and receiving study therapy or patients who have participated in a study of an investigational agent and received study therapy or used an investigational device within 4 …