Over the past two decades, several protein and genomic markers have refined the prognostic information of colorectal cancer (CRC) and helped to predict which patient group may benefit most from systemic treatment or targeted therapies. Of all these markers, KRAS represents the first biomarker integrated into clinical practice for CRC. Microarray-based gene-expression profiling has been used to identify prognostic signatures and to a lesser degree predictive signatures in CRC; however, common challenges with these types of studies are clinical study design, reproducibility, interpretation and reporting of the results. We focus on the clinical application of a range of published prognostic and predictive protein and genomic markers in CRC and discuss the different challenges associated with microarray-based gene-expression profiling. While none of these genomic signatures is currently in routine clinical use in CRC, novel adaptive clinical trial designs that incorporate putative genomic prognostic/predictive markers in prospective randomized trials, will enable a clinical validation of these markers and may facilitate the implementation of these biomarkers into routine medical practice.
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