Impact of molecular biology on the clinical management of breast cancer.

The use of molecular markers is being explored in the prediction of risk of developing breast cancer, in the assessment of prognosis and in the identification of appropriate treatment. Rational selection of treatment for a patient requires an accurate assessment of the prognosis and prediction of the response to a given treatment. Neither of these is possible with current clinicopathological markers. As a result, the current management of breast cancer is empirical, based on the outcome of randomized clinical trials that examine average effects within populations. Clinicopathological factors can be used to separate patients into broad prognostic groups, and treatment decisions are made on this basis. With this approach up to 70% of patients receive adjuvant treatment that is either unnecessary or ineffective. Molecular biological markers have the potential to improve this situation. A wide range of markers have been shown to be predictors of prognosis, but added individually to current prognostic indicators they do not improve the functional accuracy of prognosis or response prediction. There is a need for a molecular prognostic index that combines the results of a number of markers and can be used in conjunction with a clinical index to produce a more useful prognosis. There is also a need for an index that will predict responses to specific treatments. The impact of molecular biology on clinical management is a revolution waiting to happen.