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Diseases & Conditions

Risk Factors for Colorectal Cancer

Who is at risk for colorectal cancer?

Every one of us is at risk for colorectal cancer. The lifetime risk is 1 in 18 people or about 6% of American men and women. Most people who develop colorectal cancer have no particular risk factors.

Although the exact cause for the development of precancerous colon polyps that lead to colorectal cancer is not known, there are some factors that increase a person’s risk of developing colorectal polyps and cancer. These risk factors include:

Age

The risk of developing colorectal polyps and cancer increases as we age. Precancerous polyps are common in people over 50 and can affect 40% of people over the age of 60. Colorectal cancer that develops from precancerous polyps is usually seen in people over the age of 60 however it can develop in younger people.

Gender

Women and men are at equal risk for the development of colorectal polyps and cancer.

Lifestyle factors

You may be at increased risk for developing colorectal cancer if you drink alcohol, smoke, don’t get enough exercise, and if you are overweight.

Smoking

Smoking increases the risk of precancerous polyps and colorectal cancer by two- to three-fold.

Obesity

Obesity has been linked to an increased risk of precancerous colon polyps and colon cancer. The risk is increased up to 2 times compared to individuals who have a normal body mass index.

Diet

A diet high in fat and calories and low in fiber, fruits and vegetables has been linked to a greater risk of developing colorectal cancer.

  • Polyps. There are a variety of polyps that can form on the inner wall of the colon or rectum. Precancerous polyps that can turn into colorectal cancer include adenomatous polyps. Adenomas are precancerous polyps that are considered precursors, or the first step toward colon and rectal cancer. Another pathway to cancer has recently been discovered and found to arise from large hyperplastic polyps or sessile serrated polyps (also known as sessile serrated adenomas). Individuals with numerous polyps, including adenomas, hyperplastic polyps, or other types of polyps such as hamartomas or juvenile polyps are often affected with a genetic predisposition to polyposis and colorectal cancer and are a special group of individuals who should be managed differently than people with only 1 to 2 colorectal polyps.
  • Inflammatory bowel disease. Ulcerative colitis and Crohn’s colitis are conditions in which the lining of the colon becomes inflamed. People with these conditions, when present for more than seven years and affecting a large portion of the colon are at greater risk for developing colorectal cancer.
  • Personal history. Research shows that some women who have a history of ovarian or uterine cancer, especially at a young age have a somewhat increased risk of developing colorectal cancer. Also, a person who already has had colorectal adenomas or cancer may develop the disease a second time.
Family history

Parents, siblings, and children of a person who has had colorectal adenomas or cancer are at least 2-3 times more likely to develop colorectal cancer themselves. Sometimes colon cancer clusters in families. In these cases, more cancers are occurring than would be expected by chance, yet they do not appear to be clearly hereditary. Very little is known about the causes of cancer in these families. It is possible that interactions are occurring between genes and the environment or among several genes. This type of moderately increased cancer risk can be called a "familial colon cancer."

About 5% to 10% of colon cancers are believed to be hereditary. Hereditary susceptibility to cancer can be inherited and can be passed on within a family. When a person has a hereditary cancer susceptibility, he or she has inherited a copy of a cancer susceptibility gene with a mutation. Individuals who inherit a mutation in a cancer susceptibility gene have a much greater chance for developing cancer. However, not everyone with a cancer susceptibility gene mutation will develop cancer.

The most common inherited colorectal cancer syndromes are hereditary nonpolyposis colorectal cancer (HNPCC), familial adenomatous polyposis (FAP), and MYH-associated polyposis (MAP). Other syndromes include juvenile polyposis syndrome (JPS), Peutz-Jeghers syndrome (PJS), and the PTEN-hamartoma tumor syndrome. Genetic testing is available for all of these syndromes.

Having one or more of these risk factors does not guarantee that you will develop colorectal cancer. However, you should talk about these risk factors with your doctor. He or she may be able to suggest ways to reduce your chances of developing colorectal cancer.

© Copyright 1995-2009 The Cleveland Clinic Foundation. All rights reserved.

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This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition. This document was last reviewed on: 7/21/2009…#11922