Triple-negative breast cancer: risk factors to potential targets

Triple-negative breast cancer has recently been recognized as an important subgroup of breast cancer with a distinct outcome and therapeutic approach when compared with other subgroups of breast cancer. Triple-negative breast cancer comprises primarily, but not exclusively, a molecularly distinct subtype of breast cancer, the basal-like subtype. We do not yet have an assay to identify basal-like breast cancer in clinical samples, so triple-negative breast cancer has become a commonly used proxy for this subtype. The molecular biology and pathophysiology of triple-negative breast cancer are not completely understood, but understanding is improving rapidly with the advent of sophisticated molecular biology platforms. Moreover, the established risk factors of breast cancer as a whole may not apply to this unique subgroup of patients. Finally, because triple-negative breast cancer is defined by the absence of a target, there are currently limitations to using a tailored therapeutic approach, leaving conventional cytotoxic therapies as the mainstay. Active preclinical and clinical research programs focus on defining the clinical behavior, delineating the risk factors, and more completely understanding the molecular biology of triple-negative breast cancer to improve prevention, optimize conventional agents, and unveil novel therapeutic targets. This CCR focus article will review the current state of the art on triple-negative breast cancer.