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Colorectal Cancer


Causes and Risks

What are the causes and risks of the disease?

Colorectal cancer is the third most common cancer. People have an increasing risk for it starting at the age of 40. People over the age of 50 account for 93% of colorectal cancer cases.

Experts believe that this slow-growing cancer begins when normal cells in the mucosa become overactive. These overactive cells form a small benign tumor called an adenoma. Abnormal cell changes continue, ultimately turning into cancer. Several genes play a role in colorectal cancer, too.

Some risk factors for the disease are:

  • small growths in the colon called colorectal polyps
  • polyp syndromes, which means that colorectal polyps form frequently
  • a family history of colorectal cancer
  • ulcerative colitis, a chronic inflammatory disease of the bowel mucus, or inflammation of the colon that results in ulcers
  • environmental factors
  • smoking

Certain foods increase the risk for getting this disease, such as:

  • eating a lot of meat
  • eating a diet high in fat and low in fiber

What can be done to prevent the disease?

Research findings show that eating a diet high in fiber and getting enough calcium can help prevent colorectal cancer. Use of aspirin and vitamin E are also associated with a lower risk of colorectal cancer.

Early diagnosis is key to preventing death from this disease. Starting at the age of 40, people should have yearly digital rectal exams and fecal occult blood tests. This screening allows early detection of colorectal polyps. These precancerous lesions can be removed before they turn into colorectal cancer.

Beginning at the age of 50, a person should have asigmoidoscopy every 3 to 5 years. A sigmoidoscopy is a procedure that allows a healthcare professional to look into the rectum and the sigmoid colon through a flexible scope.

More frequent or earlier screening may be needed for people who:

  • have a family history of colorectal cancer
  • have developed colorectal polyps. Polyps are removed during sigmoidoscopy to keep the polyps from becoming cancerous or to assess a person's future risk for cancer.

People who are at high risk for colorectal cancer because of family polyp syndrome or ulcerative colitis often choose to have the colon removed. This is called a colectomy.


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