Colon cancer screening

Screening for colon cancer; Colonoscopy - screening; Sigmoidoscopy - screening; Virtual colonoscopy - screening; Fecal immunochemical test; Stool DNA test; sDNA test; Colorectal cancer - screening; Rectal cancer - screening

Colon cancer screening can detect polyps and early cancers in the large intestine. This type of screening can find problems that can be treated before cancer develops or spreads. Regular screenings may reduce the risk for death and complications caused by colorectal cancer.

SCREENING TESTS

There are several ways to screen for colon cancer.

Stool test:

  • Polyps in the colon and small cancers can cause small amounts of bleeding that cannot be seen with the naked eye. But blood can often be found in the stool.
  • This method checks your stool for blood.
  • The most common test used is the fecal occult blood test (FOBT). Two other tests are called the fecal immunochemical test (FIT) and stool DNA test (sDNA).

Sigmoidoscopy:

  • This test uses a small flexible scope to view the lower part of your colon. Because the test only looks at the last one third of the large intestine (colon), it may miss some cancers that are higher in the large intestine.
  • Sigmoidoscopy and a stool test may be used together.

Colonoscopy:

  • A colonoscopy is similar to a sigmoidoscopy, but the entire colon can be viewed.
  • Your health care provider will give you the steps for cleansing your bowel. This is called bowel preparation.
  • During a colonoscopy, you receive medicine to make you relaxed and sleepy.
  • Sometimes, CT scans are used as an alternative to a regular colonoscopy. This is called a virtual colonoscopy.

Other test:

  • Capsule endoscopy involves swallowing a small, pill-sized camera that takes a video of the inside of your intestines. The method is being studied, so it is not recommended for standard screening at this time.

SCREENING FOR AVERAGE-RISK PEOPLE

There is not enough evidence to say which screening method is best. But, colonoscopy is most thorough. Talk to your provider about which test is right for you.

Both men and women should have a colon cancer screening test starting at age 50. Some providers recommend that African Americans begin screening at age 45.

With a recent increase in colon cancer in people in their 40s, the American Cancer Society recommends that healthy men and women start screening at age 45. Talk to your provider if you're concerned.

Screening options for people with an average risk for colon cancer:

  • Colonoscopy every 10 years starting at age 45 or 50
  • FOBT or FIT every year (colonoscopy is needed if results are positive)
  • sDNA every 1 or 3 years (colonoscopy is needed if results are positive)
  • Flexible sigmoidoscopy every 5 to 10 years, usually with stool testing FOBT done every 1 to 3 years
  • Virtual colonoscopy every 5 years

SCREENING FOR HIGHER-RISK PEOPLE

People with certain risk factors for colon cancer may need earlier (before age 50) or more frequent testing.

More common risk factors are:

  • A family history of inherited colorectal cancer syndromes, such as familial adenomatous polyposis (FAP) or hereditary nonpolyposis colorectal cancer (HNPCC).
  • A strong family history of colorectal cancer or polyps. This usually means close relatives (parent, sibling, or child) who developed these conditions younger than age 60.
  • A personal history of colorectal cancer or polyps.
  • A personal history of long-term (chronic) inflammatory bowel disease (for example, ulcerative colitis or Crohn disease).

Screening for these groups is more likely to be done using colonoscopy.

Colonoscopy

There are 3 basic tests for colon cancer; a stool test (to check for blood), sigmoidoscopy (inspection of the lower colon), and colonoscopy (inspection of the entire colon). All 3 are effective in catching cancers in the early stages, when treatment is most beneficial.

Large intestine anatomy

One of the important jobs of the large intestine is to absorb the remaining water from the food residue passing through the intestines. The residue that is left remains in a semisolid state and is propelled toward the rectum by peristalsis. Through reflexes which are triggered by a full colon, feces is eliminated from the body.

Sigmoid colon cancer - X-ray

A barium enema in a patient with cancer of the large bowel (sigmoid area).

Fecal occult blood test

A fecal occult blood test is a noninvasive test that detects the presence of hidden blood in the stool. Blood in the stool that is not visible is often the first, and in many cases the only, warning sign that a person has colorectal disease, including colon cancer.

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