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Beginning at age 50, both men and women at average risk for developing colorectal cancer should use one of the screening methods below. The procedures that are designed to find polyps and suspicious tissues are preferred if these procedures are available to you and you are willing to have one of these more invasive procedures. Talk to your doctor about which method is best for you.

Prodedures that find polyps and suspicious tissues in the colon and rectum.

  • flexible sigmoidoscopy every 5 years
  • colonoscopy every 10 years
  • double contrast barium enema every 5 years
  • CT colongraphy (virtual colonoscopy) every 5 years

Stool tests that screen for colorectal cancer.

  • fecal immunochemical test (FIT) every year*
  • fecal occult blood test (FOBT) every year*
  • stool DNA test (sDNA), interval uncertain*

*Colonoscopy should be done if test results are positive

People should talk to their doctor about starting colorectal cancer screening earlier and/or being screened more often if they have any of the following colorectal cancer risk factors:1

  • a personal history of colorectal cancer or adenomatous polyps
  • a personal history of chronic inflammatory bowel disease (Crohns disease or ulcerative colitis)
  • a strong family history of colorectal cancer or polyps (cancer or polyps in a first-degree relative [parent, sibling, or child] younger than 60 or in 2 or more first-degree relatives of any age)
  • a known family history of hereditary colorectal cancer syndromes such as familial adenomatous polyposis (FAP) or hereditary non-polyposis colon cancer (HNPCC)

Screening Options

Stool tests that screen for colorectal cancer.

Fecal immunochemical test
The fecal immunochemical test (FIT), also called immunochemical fecal occult blood test (iFOBT), is a newer kind of test that also detects occult (hidden) blood in the stool. This test reacts to part of the hemoglobin molecule, which is found on red blood cells. The FIT is done essentially the same way as FOBT or guaiac but some people may find it easier to use because there are no drug or dietary restrictions (vitamins or foods do not affect the FIT) and sample collection may take less effort. This test is also less likely to react to bleeding from the upper digestive tract, such as the stomach.2

Fecal occult blood tests or guaiac
The fecal occult blood test (FOBT) is used to find occult (hidden) blood in feces. The FOBT detects blood in the stool through a chemical reaction. This test cannot tell whether the blood is from the colon or from other portions of the digestive tract (such as the stomach). Therefore, if this test is positive, a colonoscopy is needed.2 Guaiac based tests suffer from several key drawbacks that can reduce test sensitivity and product false positive results: 1. they cannot distinguish human heme from heme present in many foods, such as dietary meats; 2. they indiscriminately detect peroxidase activity, which is present in a variety of fruits and vegetables. And as a result, for a guaiac test to be useful, patients must eliminate these foods for several days precedeing the test, and during the three day period during which stool samples are collected.3

Stool DNA tests
Instead of looking for blood in the stool, these tests look for certain abnormal section of DNA from cancer or polyp cells. Colorectal cancer cells often contain DNA mutations (changes) in certain genes such as APC, K-ras and p53. Cells from colorectal cancer or polyps with these mutations are often shed into the stool, where tests may be able to detect them. This is a newer test, and the best length of time to go between tests is not yet clear. This test is also much more expensive then other forms of stools testing. As with other stool tests, if the results are positive, a colonoscopy is required to investigate further.2

Procedures that find polyps and suspicious tissues in the colon and rectum.

Flexible sigmoidoscopy
Flexible sigmoidoscopy allows the physician to look for early signs of colorectal cancer in the lining of the sigmoid colon and rectum. In this test, a flexible tube containing a light and a camera (sigmoidoscope) is inserted through the anus into the rectum and sigmoid colon. The sigmoidoscope is used to transmit images to a monitor. If suspicious tissue is found, the physician inserts special instruments through the tube to remove a sample for examination under a microscope (biopsy). Patients must adhere to a liquid diet for 12-24 hours before undergoing sigmoidoscopy to ensure that the colon is empty. The procedure usually takes 10 to 20 minutes and complications are rare. Studies have found that screening with flexible sigmoidoscopy can reduce CRC mortality by about 60% for cancers within reach of the instrument.Combining FOBT and flexible sigmoidoscopy follows the assumption that one test would compensate for the limitations of the other, leading to improved early detection.4,5

Colonoscopy allows the physician to view images of the entire colon and rectum using a long flexible tube with a light and camera (colonoscope). Biopsy of suspicious tissue can be performed using instruments inserted through the tube. Colonoscopy patients must adhere to a liquid diet for 1-3 days before the procedure to ensure that the colon is completely empty. Patients are given a sedative and pain reliever before undergoing the procedure. Colonoscopy usually takes 30 to 60 minutes and complications are rare. Medication or a probe can be inserted through the colonoscope to stop the bleeding if necessary.4 Findings from the National Polyp Study suggest that periodic colonoscopy could prevent 76% to 90% of colon cancer.5

Double contrast barium enema (DCBE)
This procedure is also called an air-contrast barium enema or a barium enema with air contrast. It is basically a type of x-ray test. Barium sulfate and air are used to outline the inner part of the colon and rectum to look for abnormal areas on x-rays. If suspicious areas are seen on this test, a colonoscopy will be needed.2 In double-contrast barium enema, air and a contrast solution (barium) are introduced into the large intestine and a fluoroscope is used to produce realtime images of the size, shape, and movement of the colon and rectum. Patients must refrain from eating or drinking anything after midnight on the day of the procedure. They also are given a laxative and a cleansing enema before the procedure to make sure that the colon is empty. Double-contrast barium enema results in an accurate diagnosis in about 90% of cases. It is less effective in patients with severe diverticulosis.4

CT colonography (virtual colonoscopy)
This test is an advanced type of computed tomography (CT or CAT) scan of the colon and rectum. A CT scan is an x-ray test that produces detailed crosssectional images of your body. Instead of taking one picture, like a regular x-ray, a CT scanner takes many pictures as it rotates around you. A computer then combines these pictures into images of slices of the part of your body being studied. If polyps or other suspicious areas are seen on this test, a colonoscopy will likely be needed to remove them or to explore them fully.2

1American Cancer Society Guidelines for the Early Detection of Cancer 3/5/2008.
2American Cancer Society "Detailed Guide: Colon and Rectum Cancer Can Colorectal Polyps and Cancer be Found Early" March 2008.
3Testimony of Richard C. Wender, MD, to the Practicing Physicians Advisory Council, December 16, 2002.
4Colon Cancer (Colorectal Cancer).
5Colorectal Cancer Facts and Figures, Special Edition 2005, the American Cancer Society.