“Biological markers can impact all stages of cancer research, including screening and diagnosis, characterization of tumor subtypes, prognostic indicators, and markers of response or pharmacodynamic activity of drugs. Currently single feature biological markers are already in place in many cancer treatment paradigms. Thus, the use of biological markers is not a novel idea, although novel biomarkers are being routinely identified in the laboratory. The true impact of these markers however will depend on extensive validation, a field which has lagged behind. Essentially, the application of pharmacogenomics has improved our ability to identify potential biomarkers, but the number of these biomarkers being extensively validated is comparably low.”