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When to Get a Colorectal Cancer Check

Excluding skin cancer, colorectal cancer is the third most common type of cancer in both men and women the United States. It strikes more than 140,000 Americans and kills about 50,000 every year. It's one of the most curable cancers if detected early, but it often produces no symptoms until it's beyond successful treatment. It is thought that most colon cancers develop when environmental factors interact with an person’s inherited or acquired susceptibility. Most colon cancers come from a type of growth in the large intestine called an adenomatous polyp. These polyps can slowly change, usually taking many years to develop into cancer.

That's why everyone should be aware what risk group he or she falls into and when to begin screening for colorectal cancer.

All women and men at average risk for colorectal cancer should have a screening test for colorectal cancer beginning at age 50 (colorectal cancer is rarely found in people under the age of 50).

People who are at higher risk for colorectal cancer may need to begin screening tests at a younger age. People at higher risk include:

  • Those with familial polyposis; that is, a family history of development of multiple polyps likely to become cancerous. Although only about 1 percent of all colorectal cancer patients have this gene, those who do have it have a nearly 100 percent chance of developing cancer. People with this cancer will likely die in their 40s if not treated. They should start screening in their teenage years.

  • Those with hereditary non-polyposis cancer (HNPCC, also known and Lynch syndrome), which is brought about by defective DNA repair genes. About three to five percent of people with colon cancer have this condition. People with HNPCC typically have parents or siblings who developed colorectal cancer before age 50. They should start screening in their 20s, or about 10 years before the youngest age of the family member who developed colorectal cancer.

  • Those who have had colorectal cancer or a precancerous polyp.

  • Those who have a parent, sibling, or child who has had colorectal cancer before the age of 60, or if more than one relative is affected (at any age), have a two to four times greater risk.

  • Those who have chronic inflammatory bowel disease (ulcerative colitis or Crohn's colitis), a condition that causes the colon to be chronically inflamed, have an increased risk of developing colon cancer. Screening should be started at a young age and be done more frequently.

Several methods can be used for screening. A person’s preference and the recommendation of his or her health care provider should determine which test is used and how frequently a person is screened.

Screening tests

The fecal occult blood test (FOBT) and fecal immunochemical test (FIT) look for hidden (occult) blood in stool. Blood in the stool can be caused by a variety of conditions; colorectal cancer is only one of them. The FOBT uses a chemical reaction to detect blood in small samples of stool that have been placed on a FOBT sample card. Usually two samples from each of three consecutive stools are collected at home and mailed or taken to your health care provider’s office for testing. Certain foods or drugs can affect the FOBT, so you should follow instructions on diet and medications. The FIT looks for a specific part of a human blood protein. Collecting samples for the FIT is easier (there are no drug or dietary restrictions during testing), but the test is more expensive than the FOBT. The American Gastroenterological Association (AGA) and the American Cancer Society (ACS) say that if a test is positive for blood in stool, a colonoscopy should be done to determine the source of the bleeding. It could be caused by cancer, a polyp, hemorrhoids, diverticulosis (a condition in which small pouches form at weak spots in the wall of the colon), or inflammatory bowel disease (also called colitis). If cancer or a precancerous polyp does not bleed, this test will not detect it. For people at average risk who choose this test, the ACS and the AGA recommend that it be done once a year.

Sigmoidoscopy uses a short, flexible, lighted tube tube that is inserted into the rectum and gently moved into the lower part of the colon. It is a common screening method, but only covers the lower part of the colon, representing less than half the surface at risk for developing cancer. Before this test is done, the colon and rectum must be cleaned with an enema. The ACS recommends that people at average risk have it done every five years.

Colonoscopy uses a colonoscope, a slender, flexible lighted tube that is longer than the one used for sigmoidoscopy. In a colonoscopy, the entire colon is examined. If a polyp is found, it can be removed during the colonoscopy. Before a colonoscopy, the entire colon must be cleaned with laxatives and/or enemas. A colonoscopy can be uncomfortable, so an intravenous medication is usually used to make you feel sleepy during the procedure. Colonoscopy takes about 30 minutes, longer if a polyp is removed. A colonoscopy is recommended every 10 years.

Double-contrast barium enema (DCBE) is a type of X-ray test. Barium sulfate, a chalky liquid, 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 to explore them further. This test is recommended every five years.

Newer methods of screening for colorectal cancer may be recommended as screening options.

Virtual colonoscopy (also known as CT colonography) is a three-dimensional CT scan of the colon. Some people may prefer it to a standard colonoscopy because it is not as invasive, although it still requires that the entire colon be cleaned with laxatives and/or enemas beforehand. If polyps are seen in a virtual colonoscopy, a standard colonoscopy will need to be done to remove them. This test should be done every five years.

Stool DNA tests look for certain abnormal sections of genetic material from cancer or polyp cells in the stool. These tests are not invasive and don't require any special preparation, but they are expensive. An entire stool sample is collected at home and mailed to a lab for processing. People having this test will receive a kit with detailed instructions from their doctor's office or clinic on how to collect the specimen. As with other stool tests, if the results are positive, a colonoscopy is needed to investigate further. Because this is a newer type of test, the best length of time to go between tests is not yet clear.

Screening for those at higher risk

The ACS makes the following recommendations:

  • If you have had a precancerous polyp or colorectal cancer, you should follow the recommendations of your health care provider.

  • If you have a parent or sibling who had colorectal cancer before the age of 60, or two or more close relatives who had colorectal cancer at any age, you should have a colonoscopy beginning at age 40, or 10 years before the youngest case in the immediate family. Screening by colonoscopy should continue every five years as long as the results do not show a precancerous polyp or cancer.

  • If you have a family history of familial adenomatous polyposis (FAP), you should be under the care of a specialist, and you generally should begin screenings at puberty.

  • If you have a family history of hereditary non-polyposis colorectal cancer (HNPCC), you should be under the care of a specialist, and you generally should begin screening in your early 20s, or 10 years before the youngest case in your immediate family.

  • If you have inflammatory bowel disease (chronic ulcerative colitis or Crohn's disease), you should be under the care of a specialist who can determine when screening should begin.

Online Resources

American Cancer Society  http://www.cancer.org/acs/groups/cid/documents/webcontent/003096-pdf.pdf
American Cancer Society  http://www.cancer.org/docroot/CRI/content/CRI_2_4_1X_What_are_the_key_statistics_for_colon_and_rectum_cancer.asp
American Cancer Society  http://www.cancer.org/docroot/CRI/content/CRI_2_4_2X_What_are_the_risk_factors_for_colon_and_rectum_cancer.asp
American Cancer Society  http://www.cancer.org/docroot/CRI/content/CRI_2_4_3X_Can_colon_and_rectum_cancer_be_found_early.asp

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