Colorectal cancer

Colorectal cancer, also called colon cancer or bowel cancer, includes cancerous growths in the colon, rectum and appendix.

Prevention

Most colorectal cancers should be preventable, through increased surveillance, improved lifestyle, and, probably, the use of dietary chemopreventive agents.

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• Surveillance: most colorectal cancer arise from adenomatous polyps. These lesions can be detected and removed during colonoscopy. Studies show this procedure would decrease by > 80% the risk of cancer death, provided it is started by the age of 50, and repeated every 5 or 10 years (Winawer et al 1993).
• Lifestyle: The comparison of colorectal cancer incidence in various countries strongly suggests that sedentarity, overeating (= high caloric intake), and perhaps a diet high in meat (red or processed) could increase the risk of colorectal cancer. In contrast, physical exercise, and eating plenty of fruits and vegetables would decrease cancer risk, probably because they contain protective phytochemicals. Eating whole apples, including the skin, offers some anticancer benefits (Liu et al). Accordingly, lifestyle changes could decrease the risk of colorectal cancer as much as 60-80% (Cummings and Bingham 1998).
• Chemoprevention: More than 200 agents, including the above cited phytochemicals, and other food components like calcium or folic acid (a B vitamin), and NSAIDs like aspirin, are able to decrease carcinogenesis in preclinical models: Some studies show full inhibition of carcinogen-induced tumours in the colon of rats. Other studies show strong inhibition of spontaneous intestinal polyps in mutated mice (Min mice). Chemoprevention clinical trials in human volunteers have shown smaller prevention, but few intervention studies have been completed today. Calcium and aspirin supplements, given for 3 to 5 years after the removal of a polyp, modestly decreased the recurrence of polyps in volunteers (by 15-20%). The "chemoprevention database"http://www.inra.fr/reseau-nacre/sci-memb/corpet/indexan.html shows the results of all published scientific studies of chemopreventive agents, in people and in animals.