The exact cause of colorectal cancer is not known. However, studies show that certain factors are linked to an increased chance of developing cancer in the colon or rectum. Ongoing research will help us learn more about who’s at greatest risk.
Many factors influence your risk for developing colorectal cancer. Some are factors you can’t change. Others are lifestyle choices you can change.
Risk Factors You Can’t Change
- Age. Colorectal cancer is more likely to occur as you get older. Risk for developing colorectal cancer goes up significantly after age 50 (but younger people can get colorectal cancer, too).
- History of cancer. A person who has already had colorectal cancer is at higher risk for developing it again. Women who have had ovarian or uterine cancer are at higher risk for colorectal cancer.
- History of polyps. Polyps are growths on the inner wall of the colon or rectum. They are common in people older than age 50. Most are benign (noncancerous). However, some may turn into cancer. Adenomatous polyps (also called adenomas) are most likely to become cancerous. Risk for colorectal cancer is higher in people who have had adenomas.
- History of inflammatory bowel disease (IBD). IBD includes ulcerative colitis and Crohn’s colitis (or Crohn’s disease). Ulcerative colitis causes inflammation and sores (ulcers) in the lining of the colon. Crohn’s colitis causes chronic inflammation of the gastrointestinal tract, most often the small intestine. People who have IBD are more likely to develop colorectal cancer.
- Race and ethnicity. African Americans are at greater risk of developing colorectal cancer and greater risk of dying from the disease than any other racial or ethnic group in the United States. Ashkenazi Jews may have inherited changes in their DNA that increase their risk of developing colorectal cancer.
- Family. Several risk factors are linked to family history of disease or to conditions that can be passed down in families.
- Family history of colorectal cancer or polyps. You are at increased risk if you have one first-degree relative (father, mother, brother, sister, or child) who had either colorectal cancer or polyps before age 60, or if you have two or more relatives who had either condition at any age.
- Familial adenomatous polyposis (FAP). This rare, hereditary condition causes hundreds of polyps in the colon and rectum. It can appear as early as the teen years and is very likely to lead to colorectal cancer.
- Gardner’s syndrome. Like FAP, this hereditary condition causes polyps and colorectal cancer at a young age. It can also cause noncancerous tumors in the skin, soft connective tissue, and bones.
- Hereditary nonpolyposis colorectal cancer (HNPCC). People with this hereditary condition tend to develop cancer at a young age without first having many polyps.
Lifestyle Risk Factors
- Smoking. People who have smoked are more likely than nonsmokers to get colorectal cancer and to die from the disease.
- Diet. Some evidence suggests that colorectal cancer may be linked with eating certain foods. People whose diets are high in red meats and processed meats are at higher risk. People whose diets are high in vegetables and fruits are at lower risk.
- Exercise. Some evidence suggests that colorectal cancer may be linked with being inactive. People who aren’t active are at higher risk for colorectal cancer. People who exercise regularly are at lower risk.
- Obesity. Being very overweight increases the risk for colorectal cancer.
- Alcohol. Heavy use of alcohol has been linked to colorectal cancer.
- Type 2 diabetes. People with this type of diabetes (which is influenced by lifestyle factors) are more likely to develop colorectal cancer and may do worse after diagnosis.