Risk Factors for Colorectal Cancer

A risk factor is something that increases your likelihood of getting a disease or condition.

It is possible to develop colorectal cancer with or without the risk factors listed below. However, the more risk factors you have, the greater your likelihood of developing colorectal cancer. If you have a number of risk factors, ask your healthcare provider what you can do to reduce your risk.

Risk factors for colorectal cancer include the following:

Genetic Factors

Heredity is perhaps the strongest risk factor for developing colorectal cancer. It is estimated that approximately 20% of all cases of colorectal cancer are hereditary. This risk increases if you have a primary relative (parent, sibling, child) who develops colorectal cancer.

Because hereditary colon cancer occurs at a younger age and is likely to be higher up in the colon, anyone with a history of colon cancer in more than one near relative should seek screening early. Guidelines recommend a screening at age 40 or 10 years younger than the earliest age at which a relative developed colon cancer, whichever is younger. Even in the absence of hereditary nonpolyposis colon cancer (HNPCC) and familial adenomatous polyposis (FAP), the presence of the disease before age 60 in near relatives increases one’s own risk.

The two most common forms of inherited colon cancer are:

  • Hereditary nonpolyposis colon cancer (HNPCC)—This is a fast-growing form of colorectal cancer and accounts for about 5% of all colorectal cancer cases. Typically, people with this form develop cancer in their 40s.
  • Familial adenomatous polyposis (FAP)—People with this type of colorectal cancer develop hundreds of polyps at a very young age, sometimes as early as their teens. Initially, polyps are benign but do become cancerous over time. This type of colorectal cancer is rare (1% of all colon cancer cases). But if you have these polyps, the likelihood that you will develop colon cancer is almost 100%, and many patients have most of their colon removed as a preventive measure.

Age

Colorectal cancer most commonly occurs after age 50, though certain forms of this cancer may develop earlier. However, colorectal cancer can occur at any age.

Lifestyle Factors

Colorectal cancer has been strongly associated with lifestyle factors. The following factors may increase your risk of developing colorectal cancer:

  • Diet—Diets high in fat (particularly fat from animal sources) and low in fiber have been associated with increased risk of colorectal cancer. Eating a diet that is high in fruits and vegetables may help lower the risk.
  • Lack of exercise—Regular exercise has been shown to decrease the risk of developing colorectal cancer. Even moderate exercise (30 minutes per day) is beneficial.
  • Obesity—Obesity increases the risk of colorectal cancer, particularly when weight is distributed in the waist, rather than on the hips and thighs. A high body mass index (BMI) is also associated with an increased risk.
  • Smoking—Smokers are 30%-40% more likely to die of colorectal cancer than nonsmokers.
  • Alcohol—Regular use of alcohol in smokers and diets high in fat appear to increase the risk of colorectal cancer. However, there does not seem to be an increased risk in people who drink alcohol, but eat diets high in fiber.

Gender

Both men and women develop colorectal cancers. However, men are at a slightly higher risk for developing rectal cancers, and women are at slightly higher risk for developing colon cancer.

Medical Conditions

The following medical conditions have been shown to increase the risk of developing colorectal cancer:

Ethnic Background

Incidence of colorectal cancer is most prevalent in "Westernized" countries. In the US, the rate is slightly higher for blacks than for whites.

References:

Colon carcinoma. EBSCO Dynamed website. Available at: http://www.ebscohost.com/dynamed/what.php. Accessed March 18, 2008.

National Cancer Institute website. Available at: http://www.cancer.gov/ .



Last reviewed April 2007 by Barbara Harty-Golder, MD, JD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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