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Risk factors
By Mayo Clinic staffA number of factors may contribute to the formation of colon polyps and colon cancer. They include:
- Age. The great majority of people with colon cancer are 50 or older. Your risk generally starts increasing around age 40.
- Inflammatory intestinal conditions. Long-standing inflammatory diseases of the colon, such as ulcerative colitis and Crohn's disease, can increase your risk.
- Family history. You're more likely to develop colon polyps or cancer if you have a parent, sibling or child with them. If many family members have them, your risk is even greater. In some cases this connection isn't hereditary or genetic. For example, cancers within the same family may result from shared exposure to a cancer-causing substance (carcinogen) in the environment or from similar diet or lifestyle factors.
- Smoking and alcohol. Smoking significantly increases your risk of colon polyps and colon cancer. Smokers are 20 percent more likely to develop colon cancer than are nonsmokers. Drinking alcohol, especially beer, in excess also makes it more likely that you'll develop colon polyps. If you smoke and drink, your risk increases even more.
- A sedentary lifestyle. If you're inactive, you're more likely to develop colon cancer. This may be because when you're inactive, waste stays in your colon longer.
- Weight. Being overweight or obese has been linked to an increased risk of several types of cancer, including colon cancer.
- Race. If you are black or an Ashkenazi Jew of Eastern European descent, you are at higher risk of developing colon cancer.
Inherited gene mutations
Another risk factor for colon polyps is genetic mutations. A small percentage of colon cancers result from gene mutations. Some of these cancers are autosomal dominant, meaning you need to inherit only one defective gene from either one of your parents. If one parent has the mutated gene, you have a 50 percent chance of inheriting the mutation. Although inheriting a defective gene greatly increases your risk, not everyone with a mutated gene develops cancer.
- Familial adenomatous polyposis (FAP). This is a rare, hereditary disorder that causes you to develop hundreds, even thousands, of polyps in the lining of your colon beginning during your teenage years. If these go untreated, your risk of developing colon cancer is nearly 100 percent, usually before age 40. The encouraging news about FAP is that in some cases, genetic testing can help determine whether you're at risk of the disease. People with FAP are also at risk of cancers of the small intestine, particularly in the duodenum.
- Gardner's syndrome. This less common syndrome is a variant of FAP. This condition causes polyps to develop throughout your colon and small intestine. You may also develop noncancerous tumors in other parts of your body, including your skin (sebaceous cysts and lipomas), bone (osteomas) and abdomen (desmoids).
- MYH-associated polyposis (MAP). This inherited condition is similar to FAP. People with MAP often develop multiple adenomatous polyps and colon cancer at a young age, such as in their 20s. This is a newly discovered disease and there's more that needs to be learned about it. Genetic testing can help determine whether you're at risk of MAP, which is caused by mutations in the MYH gene.
- Lynch syndrome. This condition, also called hereditary nonpolyposis colorectal cancer (HNPCC) is the most common form of inherited colon cancer. People with Lynch syndrome tend to develop relatively few colon polyps, but those polyps can quickly become malignant. Or, people with Lynch syndrome may have tumors in other organs, including the breast, stomach, small intestine, urinary tract and ovary, as well as in the colon.
- Peutz-Jeghers syndrome (PJS). This genetic condition usually begins with freckles developing all over the body, including the lips, gums and feet. Then benign polyps develop throughout the intestines. These polyps may become malignant, so people with this condition have an increased risk of colon cancer.
References
- Ahnen DJ, et al. Approach to the patient with colonic polyps. http://www.uptodate.com/home/index.html. Accessed June 15, 2009.
- Ahnen DJ, et al. Epidemiology and risk factors for colorectal cancer. http://www.uptodate.com/home/index.html. Accessed June 15, 2009.
- What I need to know about colon polyps. National Digestive Diseases Information Clearinghouse. http://digestive.niddk.nih.gov/ddiseases/pubs/colonpolyps_ez/. Accessed June 14, 2009.
- Torpy JM, et al. Colon polyps. Journal of the American Medical Association. 2008;300:1480.
- Fletcher RH. Screening for colorectal cancer: Strategies in patients at average risk. http://www.uptodate.com/home/index.html. Accessed June 14, 2009.
- Levin B, et al. Screening and surveillance for the early detection of colorectal cancer and adenomatous polyps, 2008: A joint guideline from the American Cancer Society, the U.S. Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology. CA, A Cancer Journal for Clinicians. 2008;58:130.
- Colorectal cancer screening. National Cancer Institute. http://www.cancer.gov/cancertopics/factsheet/Detection/colorectal-screening. Accessed June 15, 2009.
- How is colorectal cancer found? American Cancer Society. http://www.cancer.org/docroot/CRI/CRI_2_1x.asp?rnav=criov&dt=10. Accessed June 15, 2009.
- Seitz U, et al. Endoscopic removal of large colonic polyps. http://www.uptodate.com/home/index.html. Accessed June 15, 2009.
- How is colorectal cancer treated? American Cancer Society. http://www.cancer.org/docroot/CRI/content/CRI_2_2_4X_How_Is_Colorectal_Cancer_Treated.asp?sitearea=. Accessed June 15, 2009.
- Can colorectal cancer be prevented? American Cancer Society. Accessed June 15, 2009.
- Picco MF (expert opinion). Mayo Clinic, Jacksonville, Fla. June 19, 2009.
- MYH-associated polyposis. Cancer Net, American Society of Clinical Oncology. http://www.cancer.net/patient/Cancer+Types/MYH-Associated+Polyposis. Accessed June 19, 2009.
