Breast cancer prognostication and prediction: are we making progress?

Currently, much effort is being invested in the identification of new, accurate prognostic and predictive factors in breast cancer. Prognostic factors assess the patient's risk of relapse based on indicators such as intrinsic tumor biology and disease stage at diagnosis, and are traditionally used to identify patients who can be spared unnecessary adjuvant therapy based only on the risk of relapse. Lymph node status and tumor size are accepted as well-defined prognostic factors in breast cancer. Predictive factors, in contrast, determine the responsiveness of a particular tumor to a specific treatment. Despite recent advances in the understanding of breast cancer biology and changing practices in disease management, with the exception of hormone receptor status, which predicts responsiveness to endocrine treatment, no predictive factor for response to systemic therapy in breast cancer is widely accepted. While gene expression studies have provided important new information with regard to tumor biology and prognostication, attempts to identify predictive factors have not been successful so far. This article will focus on recent advances in prognostication and prediction, with emphasis on findings from gene expression profiling studies.