Multi-organ metastasis is the most advanced manifestation of breast cancer where the disease is widespread and metastatic tumors are found in multiple organs of the body. Despite substantial progress for women with localized disease and oligometastasis (limited metastatic spread), multi-organ metastasis remains fatal for most patients. The most common sites for metastasis in breast cancer patients are the bone, liver, lung, and brain. Bone-only metastasis is associated with the best survival, and brain-only carries the worst prognosis. Median survival for patients with multi-organ metastasis is a dismal ~10-17 months, and it affects a substantial portion (35-40%) of stage IV patients, making it a major clinical unmet need.