RT Book, Section A1 Garber, Haven R. A1 Karuturi, Meghan S. A1 Hortobagyi, Gabriel N. A2 Kantarjian, Hagop M. A2 Wolff, Robert A. A2 Rieber, Alyssa G. SR Print(0) ID 1190836453 T1 Metastatic Breast Cancer T2 The MD Anderson Manual of Medical Oncology, 4e YR 2022 FD 2022 PB McGraw Hill Education PP New York, NY SN 9781260467642 LK accessmedicine.mhmedical.com/content.aspx?aid=1190836453 RD 2024/03/29 AB KEY CONCEPTSMetastatic breast cancer (MBC) most commonly arises from prior early-stage breast cancer and is incurable, with prognosis influenced by disease subtype (hormone receptor [HR] and HER2 receptor status).Treatment of MBC is increasingly guided by disease biology, and the armamentarium of treatments includes several targeted agents, antibodies and antibody-drug conjugates, and checkpoint inhibitors.Patients can live many years with MBC and preserving quality of life, minimizing toxicity, and shared patient-physician decision making are paramount in planning the best treatment strategy.Endocrine therapy remains the backbone of treatment for HR-positive MBC and now includes CDK4/6 inhibitors as standard frontline treatment.The clinical outcomes of patients with HER2-positive MBC continue to improve because of the efficacy of therapies that target the HER2 kinase pathway including pertuzumab, ado-trastuzumab emtansine, and tucatinib.Metastatic triple-negative breast cancer remains the breast cancer subtype with the worst prognosis. However, multiple clinical trials are underway that incorporate immunotherapy, antibody-drug conjugates, and targeted therapies in an effort to improve outcomes over those achieved with standard chemotherapy.