Women's Health Specialists of St. Louis
Obstetrics and Gynecology

Articles - Colorectal Cancer

It may be a surprise for many women that the third leading cause of death from cancer is colorectal cancer. Colorectal cancer is commonly referred to as colon cancer. It is uncommon before age 40. After age 50, the risk increases greatly and the lifetime incidence for patients at average risk is 5%. Though it is common and lethal, it can also be preventable. Most colorectal cancers arise from adenomatous polyps in the colon. Over time, the cells become progressively abnormal until a cancer develops. This progression likely takes about ten years to occur. Since most cancers develop slowly and most arise from polyps, there is opportunity to intervene and remove the abnormal cells before a cancer occurs. For example, in one study, all the participants were screened by colonoscopy but only some of the participants had the polyps removed. Those patients who underwent polyp removal had a decrease in the risk of colon cancer by as much as 90% during a six year follow-up. Deciding who and when to screen, depends on the individuals risk factors. Though genetics has some role as to who might develop colon cancer, most of the risks are acquired. Risks are higher for those who lead sedentary lifestyles and eat high fat low fiber diets. Genetic factors to take into account include race and family history. Colorectal cancer is 16% higher in blacks than whites and substantially lower in Asians, Hispanics, and Native Americans. It occurs more commonly in people with a history of inflammatory bowel disease such as Crohns or ulcerative colitis.

Approximately 10% of all adults will have at least one family member with a history of colon cancer. This does not raise the risk substantially unless the relative is a first degree relative (parent, child, and sibling). One affected first degree relative doubles the risk of developing colorectal cancer. Though the majority of colorectal cancers occur in patients who are not at increased risk, there are inherited syndromes that may increase the risk for some families. Hereditary nonpolyposis colon cancer (HNPCC) or Lynch syndrome is a genetically inherited disorder which increases the lifetime risk of colon cancer to 70%. Thankfully this disorder is not common and accounts for less than 5% of all colon cancers. Families affected by this disorder tend to develop cancers of the colon earlier in life (30s and 40s) and also more frequently have cancers of the female genital tract (i.e. ovary and uterus). Genetic screening is available to confirm this disorder. Familial Adenomatous Polyposis is another familial cancer that accounts for 1% of colorectal cancers. This disorder causes the development of hundreds of polyps throughout the colon which the inevitable progression to colon cancer. As with HNPCC, this disorder is suspected only when families have multiple members affected with colon cancer prior to age 50.

The key to prevention of colon cancer is screening. All women should begin screening by age 50. Women at increased risk because of family history, should begin screening earlier. Women who have had breast, ovarian, or uterine cancer should also begin screening earlier. Screening may be performed in one of three ways: yearly fecal occult blood test, sigmoidoscopy, or colonoscopy. The American College of Gatroenerology now considers colonoscopy as the preferred screening test. This test is preferred because the whole colon is visualized and polyps may be removed at the time of the procedure. For patients at low risk, the procedure need only be performed every ten years. The drawback of colonoscopy is the bowel prep required and the 0.1% risk of major complications. Though fecal occult blood testing and sigmoidoscopy are less invasive, they are more likely to be falsely negative and a positive test requires further evaluation with colonoscopy. Depending on a womans risk factors and other health history, the physician may recommend a specific screening tool over another. In the end, this is a very preventable cancer, if women take the time to be screened.