Molecular Stratification of Triple-Negative Breast Cancers

Research focused on the analysis and classification of breast tumors, primarily using DNA microarrays and patterns of gene expression, has resulted in distinct tumor subtypes. Although no knowledge of patient survival or outcomes was used to derive these gene descriptions, these different classes based upon patterns of gene expression have important prognostic implications. Predictive markers in estrogen receptor-negative and triple-negative disease will be particularly important because in the absence of therapy, these tumor subtypes tend to have a poor prognosis. In addition, the claudin-low subgroup has been found to be common within the triple-negative cancers and may have further prognostic and therapeutic implications. Patients with triple-negative breast cancer do benefit from chemotherapy, but better treatment options are needed that are less toxic, reduce the risk of disease progression, and are more targeted to this patient population. Potential treatments include poly (ADP-ribose) polymerase inhibitors, and therapies that target cancer stem cells could also have an important impact in these patients. This article will focus on the molecular stratification of triple-negative breast cancers and the therapeutic implications of these classifications.