Prognostic and predictive markers in colorectal cancer

Prognostic and predictive biomarkers have revolutionized medicine by allowing individualized treatment decisions. Most notably in oncology, where treatment can be associatedwith significant toxicities and often unpredictable outcomes, there is a need to isolate patients that are likely to benefit from an intervention. In colorectal cancer, there are many markers being investigated but only a few that have sufficient evidence to warrant use in clinical practice. This paper will review these prominent biomarkers in both adjuvant and metastatic colorectal cancer and summarize the data regarding their utility. Themarkers reviewed include microsatellite instability, 18qLOH, gene profile assays such as ColoPrint and Oncotype DX, Kras, Braf, thymidylate synthase, and circulating tumor cells.The paper will also discuss optimal clinical trial design, with a focus on different validation strategies for emerging biomarkers. By highlighting the pertinent literature, the hope is to facilitate a personalized approach to colorectal cancer care.