Colorectal cancer screening - methodology.

Colorectal cancer (CRC) is a major problem worldwide with the highest incidence being found in developed countries, and is the 3rd most common cancer in Scotland. Patients do not generally have symptoms related to CRC until late in the disease process, so there has been much interest in developing screening programmes to detect CRC early. Most commonly, screening involves the identification of occult blood in stool samples. Alternatives include flexible sigmoidoscopy, colonoscopy, radiological investigation and the identification of DNA mutations or proteins in stool. Candidate markers for mutation identification are K-ras, BRAF, p53 and APC which may be used alone or in combination to identify those with colorectal cancer.