Molecular tests as prognostic factors in breast cancer.

In early breast cancer, prognostic tests are used to guide decisions on adjuvant systemic hormonal therapy, chemotherapy and targeted therapy treatment. This has led to large research efforts to identify novel prognostic markers in breast cancer. At present, the tissue factors used to guide treatment of breast cancer patients are tumor size, lymph node status, histologic grade, ER status, PR status, and HER2 status; in addition, multigene-expression-based prognostic tests are rapidly emerging. While identification of prognostic gene expression profiles has been successful, it has not been possible yet to identify robust clinically useful predictors of response to systemic treatment. As a result of rapid advances in technology and bioinformatics, it has become possible to analyze large series of breast carcinomas using high-throughput genetic techniques, including whole genome sequence analysis and gene expression profiling. These genomic studies will lead to the development of additional prognostic and predictive tissue-based tests. The most important aspects of the currently used tissue-based prognostic and predictive tests and the research in this area are reviewed.