Cancers of the Colon & Rectum

Cancer in the colon or rectum (colorectal cancer) is a condition in which cells that line the colon or rectum mutate in ways that allow them to multiply in an uncontrolled way and invade other tissues. These rapidly growing cells then form into masses of tissue that can interfere with the normal function of the colon or rectum, causing bleeding or obstruction. Colorectal cancer takes many years to develop. Most colorectal cancers arise from polyps, which are small mushroom-type growths on the interior lining of the colon or rectum. Polyps are usually present for many years before the cells within them further mutate to allow the cancerous behavior of invasion and spreading to other tissues to become apparent.

Several lifestyle factors have been shown to affect one’s risk of forming colorectal cancer, including obesity, inadequate physical activity, and diets high in red meat and low in vegetables.

As with most other cancers, advancing age is the biggest risk factor for cancers of the colon or rectum. Men are at higher risk than women, but this gender difference is modest compared to other cancers. Blacks are at higher risk and Hispanics at lower risk. Those with a history of colorectal cancer or colorectal polyps in their family (first degree relatives) are at twice the risk of those with no family history, and are at risk at a younger age. Five to 10% of colon cancers are thought to be caused by inherited predispositions which may be detected by genetic testing.

 Several lifestyle factors have been shown to affect one’s risk of forming colorectal cancer, including obesity, inadequate physical activity, and diets high in red meat and low in vegetables. Taking estrogen replacement therapy, aspirin or other non-steroidal anti- inflammatory (NSAID) drugs reduces risk.

Randomized, controlled trials have proven that screening for blood in the stool (Fecal Occult Blood Testing with colonoscopic follow-up of all positive tests) reduces the risk of dying of colorectal cancer. The best evidence from many studies concludes that endoscopic screening (sigmoidoscopy or colonoscopy) can substantially reduce the risk of dying from colorectal cancer. Because endoscopic examinations can also allow for polyp removal, endoscopic colorectal screening is both an early detection method and also a cancer prevention method. Research studies on other screening methods, including virtual colonoscopy and testing stool samples for abnormal genes, have not yet shown to be ready for recommendation to the general public. The identification and removal of colorectal polyps is the single most effective strategy to prevent colorectal cancer.

The identification and removal of colorectal polyps is the single most effective strategy to prevent colorectal cancer.

Colorectal cancer death rates will likely continue to fall in Colorado in the years to come. If we can reverse the adverse obesity trends in Colorado and increase colorectal screening rates, we could see substantial reductions in colorectal cancer death rates in the years to come.