Introduction

Biomarkers may be valuable in diverse aspects of both the investigation and treatment of gastrointestinal tumours. Useful in diagnosis, in screening and surveillance and in the study of the molecular epidemiology of tumours, biomarkers may have additional value in the treatment of such tumours by acting as surrogate end-points in clinical trials. They can also be used as predictors of survival after surgical treatment.

In diagnosis for example, some have advocated the use of serum markers – a typical example being α-fetoprotein (AFP) for the detection of hepatocellular carcinoma in cases of cirrhosis associated with chronic hepatitis B or C viral infections. Perhaps the main role of the serum biomarkers used currently in clinical practice is for monitoring responses to chemotherapy and for the detection of tumour recurrence at an early stage. Good examples of the use of biomarkers in screening and surveillance include the identification of adenomas in the colon during colonoscopy or sigmoidoscopy and their removal to prevent the progression to carcinoma. Examining the extent of intestinal metaplasia in different populations at risk from gastric carcinoma, and its molecular pathology, gives insight into the size of such population risks. Surrogate end-points in the chemoprevention of colorectal carcinoma include the detection of adenomas at endoscopy. Similarly, aberrant crypt foci can be detected and used as surrogate end-points, now that magnifying endoscopy is becoming a reality.