Triple-Negative Breast Cancers: Systematic Review of the Literature on Molecular and Clinical Features with a Focus on Treatment with Innovative Drugs

Triple-negative breast cancer (TNBC) accounts for 15-20% of diagnosed breast tumours, with higher incidence in young and African-American women, and it is frequently associated with BRCA germline mutations. Chemotherapy is the only well-established therapeutic option in both early- and advanced-stages of the disease. TNBC tumours relapse earlier after standard anthracycline- and/or taxane-based chemotherapy treatments, generally within 1-3 years after the diagnosis, and often develop visceral metastases, representing the subtype with a worse prognosis among all breast cancers. In the present review, we will provide an updated overview of the available results of recent clinical trials for this disease and we will describe the implications of the known molecular pathways representing novel targets for development of future therapies for TNBC patients. Over the past decade, the advent of gene expression micro-array technology has led to the identification of different actionable targets including various genomic alterations, androgen receptor, PARP, PI3K, VEGF and other proteins of the angiogenic pathway. Thus, novel targeted drugs have been tested in clinical trials reporting promising results in specific TNBC molecular subgroups. Although cytotoxic chemotherapy remains the mainstay of treatment for TNBC patients, the identification of novel 'drugable' targets and pathways for developing personalized treatments represents a promising investigational approach in the management of the TNBC subtype.