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Colorectal cancer

Colorectal cancer risk factors

Each year, more than 140,000 Americans are diagnosed with colorectal cancer. No one knows if or when cancer in the colon or rectum will develop, but understanding the risk factors for colorectal cancer may help you take measures to reduce the likelihood of getting the disease. Patients with a higher risk should consult their doctor about when to get a colonoscopy or a stool test, which may help spot early signs of the disease.

What causes colorectal cancer?

Colorectal cancer forms when the DNA in cells in the colon or rectum develop mutations that may make them unable to control growth and division. In many cases, these mutated cells die or are attacked by the immune system. But some mutated cells may escape the immune system and grow out of control, forming a tumor in the colon or rectum.

The exact cause of colorectal cancer is not known, but certain risk factors are strongly linked to the disease, including diet, tobacco smoking and heavy alcohol use. Also, people with certain hereditary cancer syndromes or a family history of colorectal cancer have a high risk of developing the disease.

Known risk factors for colorectal cancer include:

Genetics

Family history: Although the reasons are not clear in all cases, inherited genes, shared environmental factors or a combination of these influences may increase your colorectal cancer risks. Your family history may determine when your doctor will recommend a colonoscopy to screen for colorectal cancer. For example, if your father was diagnosed with colorectal cancer at 50, your doctor may recommend you get a colonoscopy at 40.

Inherited syndromes: The two most common inherited syndromes linked with colorectal cancers are familial adenomatous polyposis (FAP) and hereditary non-polyposis colorectal cancer (HNPCC). Other syndromes that may increase the risk of developing colorectal cancer include Lynch Syndrome, Turcot Syndrome and Peutz-Jeghers Syndrome.

Racial and ethnic background: African Americans have the highest incidence of colorectal cancer in the United States. Ashkenazi Jews also have a higher risk of developing the disease. If you are in one of those ethnic groups and have no other risk factors, your doctor may suggest getting a colonoscopy at age 45 rather than 50, as is recommended for most average-risk patients.

Learn more about genetic testing

Lifestyle

Diet: Diets that are high in red and processed meats (e.g., beef, lamb, hot dogs) may increase your colorectal cancer risks. Frying, grilling, broiling or other methods of cooking meats at very high temperatures create chemicals that may also contribute to an increased risk. A diet rich in fruits, vegetables and high-fiber grains may help reduce your risk of developing colorectal cancer.

Inactive lifestyle: Individuals who live a sedentary lifestyle have an increased chance of developing colorectal cancer.

Smoking: Some of the cancer-causing substances associated with smoking may be swallowed, potentially increasing the risk of developing colorectal cancer.

Alcohol use: Heavy alcohol use may lead to an increased risk of colorectal cancer.

General

Age: Although colorectal cancer may occur at any age, the chances of developing the disease may dramatically increase after the age of 45. Nearly 95 percent of all colorectal cancer cancers occur in patients 45 or older. The median age of a patient diagnosed with colorectal cancer is 68, according to the National Cancer Institute.

History of colorectal cancer or polyps: If you have had colorectal cancer before, you are more likely to develop cancer in other areas of the colon and rectum. Or you may experience a recurrent cancer, which is a malignancy that reappears at or near the same location as the original tumor. You may also be at a higher risk of colorectal cancer if your doctor found polyps during a colonoscopy, even if those polyps were removed and/or benign.

History of inflammatory bowel disease (IBD): Having IBD, including ulcerative colitis and Crohn's disease, may increase your chances of developing colorectal cancer. Your risk may be higher the longer you have experienced IBD and depending on how much of your colon is affected.

Obesity: Being overweight may increase your risk of developing colorectal cancer.

Type II diabetes: This condition is associated with a higher risk of rectal cancer. It may also affect your prognosis.

Next topic: What are the symptoms of colorectal cancer?