THE ROLE OF PROGNOSTIC AND PREDICTIVE MARKERS IN CANCER

New genomic and proteomic technologies have led to important therapeutic advances in oncology. This article describes how the discovery of molecular prognostic markers to classify an individual patient's risk of disease events and predictive markers to classify response to specific treatment options are used to guide the selection of treatment and identify targets for the development of new molecular targeted therapies. Prognostic markers can be used to determine the need for further treatment. Patients at very low risk of disease events can safely avoid treatment if risks of adverse events outweigh the estimated benefits. Alternatively, high risk patients may benefit from a more aggressive treatment regimen. Predictive markers are used to select the most appropriate treatment by identifying patients most likely to respond and avoiding treatment for patients unlikely to respond or those at unacceptably high risk of adverse events. The clinical value of molecular markers depends on a series of factors: the reproducibility of the laboratory methods used for marker measurement; the accuracy of the marker to classify patient prognosis or response to treatment compared to conventional clinico-pathological criteria; its validity when used in independent populations; and the impact of using this information to guide treatment selection on patient outcomes. Randomised control trials are essential to assess the effectiveness and optimal use of prognostic and predictive markers and biomarker guided therapies. (author abstract)