Colorectal cancer is the third most common cancer in the U.S., with Americans facing a lifetime chance of 5 - 6% for this cancer. Men and women are at equal risk. Each year, about 108,000 Americans are diagnosed with colorectal cancer, and about 50,000 people die from the disease. About 73% of cancers occur in the colon and 27% in the rectum.
Colorectal cancer risk increases with age. More than 90% of these cancers occur in people over age 50.
African-Americans have the highest risk of being diagnosed with, and dying from, colorectal cancer. Among Caucasians, Jews of Eastern European (Ashkenazi) descent have a higher rate of colorectal cancer. Asian Americans/Pacific Islanders, Hispanics/Latinos, and American Indians/Alaska Natives have a lower risk than Caucasians.
About 20 - 25% of colorectal cancers occur among people with a family history of the disease. (Seventy-five percent of cases are due to other causes.) People who have more than one first-degree relative (sibling or parent) with the disease are especially at high risk. The risk is even higher if the relative was diagnosed with colorectal cancer before the age of 60.
About 5 - 10% of patients with colorectal cancer have an inherited genetic abnormality that causes the disease. Syndromes associated with genetic mutations include familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer.
The risks for colon cancer are far higher in industrialized nations than less developed countries. A Western lifestyle, being sedentary, smoking, and having excess weight have all been associated with increased risk for colorectal cancer. (However, about 75% of cases occur without a known predisposing factor.)
Dietary Factors. A diet high in red and processed meats increases the risk for colorectal cancer. Diets high in fruits and vegetables appear to be associated with reduced risk. It is not clear whether fiber consumption affects colorectal cancer risk. It is also not clear whether there is an association between colorectal cancer risk and vitamin deficiencies such as folic acid, a type of vitamin B. Recent studies have not shown that taking folic acid supplements lowers the risk of developing colorectal cancer.
Alcohol and Smoking. Alcohol use and smoking are associated with an increased risk for colorectal cancer. Patients who smoke and drink may also be diagnosed with colorectal cancer at a younger age than non-drinkers and non-smokers.
Obesity. Obesity is associated with an increased risk for colorectal cancer, especially for men.
Physical Inactivity. A sedentary lifestyle increases the risk of developing colorectal cancer. Regular exercise may help reduce risk.
Adenomatous Polyps. People who have had adenomatous polyps (adenomas) have an increased risk of developing colorectal cancer. When these polyps are detected during colorectal screening, as colonoscopy, they can be removed before they turn cancerous.
Inflammatory Bowel Disease. Inflammatory bowel diseases include Crohn's disease and ulcerative colitis. The long-term inflammation caused by these chronic disorders can increase the risk for colorectal cancer, particularly with all ulcerative life as Inflammatory bowel disease (IBD) is not the same as irritable bowel syndrome (IBS). IBS does not increase colorectal cancer risk.
Diabetes. Many studies have identified an association between type 2 diabetes and colon cancer. Both diseases share common risk factors of obesity and physical inactivity, but diabetes itself is a risk factor for colorectal cancer.
The best way to prevent colorectal cancer is to engage in a healthy lifestyle: Exercising regularly, eating a healthy diet low in meat and high in fruits and vegetables may help reduce the risk for colon cancer. Do not smoke, and do not drink alcohol in excess. It is also important to have regular colorectal cancer screenings. [See Diagnosis and Screening section.]
Researchers have been investigating other possible protective measures. These include:
Nonsteroidal Anti-Inflammatory Drugs (NSAIDs). Nonsteroidal anti-inflammatory drugs (NSAIDs) are very common pain relievers that are available over-the-counter and by prescription. They include aspirin, ibuprofen (Motrin), naproxen (Aleve), and the COX-2 inhibitor celecoxib (Celebrex). Several studies have reported that NSAIDs help reduce the risk of colorectal cancer. However, regular use of NSAIDs, even in low doses, can increase the risk of gastrointestinal bleeding and stomach ulcers. Long-term use of NSAIDs can also increase the risk for heart attack and stroke, especially in people who have a history of heart disease.
The U.S. Preventive Services Task Force (USPSTF) does not recommend the routine use of aspirin and other NSAIDs to prevent colorectal cancer in people at average risk for this disease. (This recommendation does not apply to people who have a family history of colorectal cancer or who are at high risk for developing colorectal cancer due to other risk factors.) Due to the risks of regular use of these drugs, the American Cancer Society and other professional associations also recommend against the use of NSAIDs, or other types of medications, for colorectal cancer prevention.
Hormone Replacement Therapy (HRT). There is some evidence that hormone replacement therapy (HRT) reduces the risk of colon cancer in postmenopausal women. HRT, however, can increase the risk for breast and uterine cancer and blood clots. For this reason, doctors do not recommend HRT for colorectal cancer prevention.
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