This study will enroll subjects who are female aged > 18 years at the time of informed consent with histologically confirmed diagnosis of breast cancer (unresectable or metastatic stage IV breast cancer). Subjects must have measurable disease and be a candidate for palliative stereotactic body radiation therapy (SBRT). Subjects must have Eastern Cooperative Oncology Group Performance Status (ECOG PS) of 0, 1, or 2 and adequate hematologic, hepatic, renal, and coagulation function. Subject must also have received two prior lines of FDA-approved therapy. Triple negative patients must have had prior exposure to taxane therapy either in the neoadjuvant/adjuvant or metastatic setting. ER + positive patients must have had prior cyclin dependent kinase (CDK) 4/6 inhibitor therapy. Her2 overexpressed patients must have had prior therapy with trastuzumab and ado-trastuzumab (TDM-1).
This is a phase 2, open-label, single-arm trial designed to evaluate the efficacy and safety of stereotactic body radiation therapy (SBRT) in combination with pembrolizumab following disease progression after two prior lines of standard therapy in unresectable metastatic stage IV breast cancer