Clinical application of molecular profiling in breast cancer

Breast cancer is the leading type of cancer and second leading cause of cancer death in women. Breast cancer mortality has declined over the past 10 years largely due to early detection by mammographic screening, but also in part due to the increasing use of adjuvant hormonal therapy and chemotherapy. Indications for adjuvant chemotherapy have now expanded to include women who are at low risk of recurrence, resulting in overtreatment of most women to benefit a few, particularly those with favorable clinical features. New techniques have been evaluated that identify specific molecular signatures that may more accurately predict prognosis than clinical features, and that may also identify individuals who are more likely to benefit from endocrine therapy and/or chemotherapy. This review will focus on the clinical applications of these novel techniques reported to date, and how this may lead to the incorporation of molecular diagnostics into clinical practice. Two prospective, multicenter, multinational Phase III trials evaluating tumor genomic profiling in breast cancer are currently in development, and will be initiated within the forthcoming year. The completion of these important studies will represent the first step toward integrating molecular profiling into treatment selection for adjuvant therapy in breast cancer.