Systemic therapies are drugs that spread throughout the body to treat cancer cells wherever they may be. They include chemotherapy, hormonal therapy, targeted drugs, and immunotherapy. Memorial Sloan Kettering is a leading center for the development of innovative systemic therapies for breast cancer. After surgery, many women benefit from adjuvant systemic therapy. The goal of this treatment is to reduce the risk of breast cancer recurring or metastasizing. Treatment of breast cancer consists of drug therapies such as chemotherapy, antihormone therapy, and targeted therapies, with improved prognosis due to advances in the diagnosis and treatment of breast cancer, physicians and therapists now also focus on aspects such as quality of life and the management of side effects from breast cancer treatment. Women with metastatic breast cancer may receive various systemic therapies to control the disease. These include hormonal therapy, biologics, immunotherapies, other targeted agents, or combinations of these. Systemic treatment can be stratified into neoadjuvant, adjuvant and metastatic settings, with each having a distinct goal. The objective of neoadjuvant treatment is to downgrade the tumor in order to facilitate breast-conserving surgery and to guide postoperative chemotherapy.