Cancer of the colon and rectum (colorectal cancer) continues to be one of the leading causes of cancer morbidity and mortality worldwide with more than 1.2 million new cases and 609,000 deaths annually (1). CRC refers to all malignant tumours that develop in the region of colon and rectum. Tumours that are located in the caecum, ascending- and the transverse colon are called proximal cancers, and those located in the descending colon, sigmoid colon and rectum are known as distal cancers.
The majority of CRC cases are classified as sporadic, and 75% of them are estimated to develop in people who are considered to be at moderate risk of developing this disease. Only about 20% of CRC cases are found among people known to have some degree of family history. The remaining 80% occur in patients with a predisposing inflammatory bowel disease (ulcerative colitis), or any of the known gene mutations (familial adenomatous polyposis, or hereditary, non-polyposis colorectal cancer) (2&3). Early case control studies showed that the risk of developing CRC is more than double among the subjects of first-degree relatives with the same disease (4).
It is currently estimated that at least 95% of all CRC cases develop from clearly identifiable precursors, such adenomatous polyps and flat adenomas (5). This progressive adenoma-to-cancer pathogenesis is based on extensive population studies, according to which the bowel cancer risk is many times higher in people who suffer from hereditary polyposis syndromes, as well as on follow-up studies indicating that the development of CRC was reduced by 60 to 90% among individuals who had undergone an endoscopic removal of their polyps (polypectomy) (6). Well-designed case-control studies also show conclusively that the removal of polyps in sigmoidoscopy resulted in reduction of CRC mortality by more than 60% during 10 years of follow-up, as compared to the respective control subjects (7).
Colorectal cancer refers to all malignant tumors that develop in the region of colon and rectum. Tumors that are located in the caecum, ascending- and the transverse colon are called proximal cancers, and those located in the descending colon, rectum and sigma are known as distal cancers. According to this definition, CRCs do not include bowel cancers that are located in the small intestines or in the anal region.