1. What is colorectal cancer?

Colorectal cancer is a disease in which cells in the colon or rectum become abnormal and divide without control or order, forming a mass called a tumor. (The colon and rectum are parts of the body’s digestive system that remove nutrients from food and water and store solid waste until it passes out of the body.) Cancer cells invade and destroy the tissue around them. They can also break away from the tumor and spread to form new tumors in other parts of the body.

Colorectal cancer is the fourth most common type of cancer and the second leading cause of cancer death in the United States. The number of new cases and deaths resulting from this disease is decreasing. Still, over 135,000 new cases are diagnosed and more than 56,000 people die from colorectal cancer each year.

2. Who is at risk for colorectal cancer?

The exact causes of colorectal cancer are not known. However, studies show that certain factors increase a person’s chance of developing colorectal cancer:

• Age—Colorectal cancer is more likely to occur as people get older. Although the disease can occur at any age, most people who develop colorectal cancer are over the age of 50.
• Polyps—Polyps are benign (noncancerous) growths that protrude from the inner wall of the colon or rectum. They are relatively common in people over age 50. Because experts believe most colorectal cancers develop in polyps, detecting and removing these growths may be a way to help prevent colorectal cancer. The procedure to remove polyps is called a polypectomy.

  Familial adenomatous polyposis, or FAP, is a rare, inherited condition in which hundreds of polyps develop in the colon and rectum. Because this condition is extremely likely to lead to colorectal cancer, it is often treated with surgery to remove the colon and rectum (colectomy). Rectum-sparing surgery may be an option. Researchers are studying the use of anti-inflammatory drugs as a treatment for FAP.

• Personal history—A person who has already had colorectal cancer may develop colorectal cancer a second time. Also, research studies show that women with a history of ovarian, uterine, or breast cancer have a higher-than-average chance of developing colorectal cancer.
• Family history—Close relatives (parents, siblings, or children) of a person who has had colorectal cancer are somewhat more likely to develop this type of cancer themselves, especially if the family member developed the cancer at a young age. If many family members have had colorectal cancer, the chances increase even more.
• Ulcerative colitis or Crohn’s colitis—Ulcerative colitis is a condition that causes inflammation and sores (ulcers) in the lining of the colon. Crohn’s colitis (also called Crohn’s disease) causes chronic inflammation of the gastrointestinal tract, most often the small intestine (the part of the digestive tract that is located between the stomach and the large intestine). People who have ulcerative colitis or Crohn’s colitis may be more likely to develop colorectal cancer than people who do not have these conditions.
• Diet—Some evidence suggests that the development of colorectal cancer may be associated with a diet that is high in fat and calories and low in foods with fiber, such as whole grains, fruits, and vegetables. Researchers are exploring what role these and other dietary components play in the development of colorectal cancer.
  
  3. What is screening, and why is it important?

Screening means checking for health problems before they cause symptoms. Screening can find some cancers before they spread to other parts of the body.

Colorectal cancer screening is used to detect cancer, polyps that may eventually become cancerous, or other abnormal conditions. If screening detects an abnormality, diagnosis and treatment can occur promptly. Colorectal cancer is generally more treatable when it is found early.

4. What methods are used to screen people for colorectal cancer?

Health care providers may suggest one or more of the tests listed below for colorectal cancer screening.

• A fecal occult blood test (FOBT) checks for hidden blood in the stool. Studies have proven that this test, when performed every 1 to 2 years in people age 50 to 80, reduces the number of deaths due to colorectal cancer.
• A sigmoidoscopy is an examination of the rectum and lower colon using a lighted instrument called a sigmoidoscope. Sigmoidoscopy can find precancerous or cancerous growths in the rectum and lower colon. Studies suggest that regular screening with sigmoidoscopy after age 50 can reduce the number of deaths from colorectal cancer.
• A colonoscopy is an examination of the rectum and entire colon using a lighted instrument called a colonoscope. Colonoscopy can find precancerous or cancerous growths throughout the colon, including the upper part of the colon, where they would be missed by sigmoidoscopy. However, it is not known whether this benefit outweighs the increased risks of colonoscopy, which include bleeding and puncturing of the lining of the colon. More research is needed to address these issues.
• A double contrast barium enema (DCBE) is a series of x-rays of the entire colon and rectum. The x-rays are taken after the patient is given an enema with a barium solution and air is introduced into the colon. The barium and air help to outline the colon and rectum on the x-rays. Research shows that DCBE is more effective at detecting larger growths than smaller ones.

A digital rectal exam (DRE) is often part of a routine physical examination. In a DRE, the health care provider inserts a lubricated, gloved finger into the rectum to feel for abnormal areas. The test is often used to examine nearby structures, such as the prostate in men. Unlike the colorectal cancer screening tests described above, DRE allows for examination of only the lowest part of the rectum.

Scientists are still studying colorectal cancer screening methods, both alone and in combination, to determine how effective they are. Studies are also under way to clarify the risks of each test.

See question 5 for a table outlining some of the advantages and disadvantages of colorectal cancer screening tests. Additional information about these tests is available from the National Cancer Institute’s (NCI) Web site at http://cancer.gov/colon on the Internet.

5. How can people and their health care providers decide which colorectal cancer screening test to use and how often to be screened?

Several major organizations, including the U.S. Preventive Services Task Force (a group of experts convened by the U.S. Public Health Service) and the American Cancer Society, have developed guidelines for colorectal cancer screening. Although their recommendations vary regarding which screening tests to use and how often to be screened, all of these organizations support screening for colorectal cancer.

People should talk with their health care provider about when to begin screening for colorectal cancer, what tests to have, the benefits and risks of each test, and how often to schedule appointments.

The decision to have a certain test will take into account several factors:

• Person’s age, medical history, family history, and general health;
• Accuracy of the test;
• Risks associated with the test;
• Preparation required before the test;
• Sedation necessary during the test;
• Followup care after the test;
• Convenience of the test; and
• Cost and insurance coverage of the test.

The following table outlines some of the advantages and disadvantages of the colorectal cancer screening tests described in this fact sheet.

Table: Advantages and Disadvantages of Colorectal Cancer Screening Tests

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For more information on colorectal cancer, please visit the  Colorectal Cancer Home Page.

Published and reviewed by NCI on 04/03/2002