Biomarkers in Gastrointestinal Cancer: Focus on Colon, Pancreatic and Gastric Cancer

Personalized cancer medicine based on genetic profiling of individual tumors is regarded as the treatment strategy of the future. The targeted drugs for the treatment of cancer have rapidly developed. However, our understanding (at the molecular level) of the precise role that potential targets have in tumorigenesis, and the survival dependence of tumors on these components, has not progressed at the same rate (De Roock et al., 2011). Since patient selection for therapy remains problematic, there has been an increasing interest in biomarkers of cancer risk in predicting future patterns of disease. In the broadest sense, a biomarker is any biological, chemical, or biophysical indicator of an underlying biological process. From a medical perspective, a biomarker is a physiological characteristic that is indicative of health and disease. A cancer biomarker has been defined as “a molecular, cellular, tissue, or process-based alteration that provides indication of current, or more importantly, future behavior of cancer” (Hayes et al., 1996). Cancer biomarkers are employed across the entire healthcare spectrum from the cancer biological research laboratory to patient monitoring in the clinic. Clinical applications include disease risk stratification, chemoprevention, disease screening, diagnosis and prognosis/prediction, treatment planning and monitoring, and posttreatment surveillance. Cancer biomarkers have contributed greatly to our current understanding of the heterogeneous nature of specific cancers and have led to improvements in treatment outcomes. However, full adoption of cancer biomarkers in the clinic has been slow to date, and only a limited number of cancer biomarker products are currently in routine use (http://www.insightpharmareports.com/reports_report.aspx?r=559&id=78452). Two primary challenges in developing cancer biomarkers are the discovery of candidate markers and the validation of those candidates for specific uses. The discovery process depends on the technologies available, and their sensitivity and specificity, to investigate the complex biochemistry of health and disease in order to identify differences that can be detected consistently in diverse populations. The validation process is also arduous and costly, often