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.
Colon cancer is one of the leading causes of cancer-related deaths in the United States. The good news is that earlier diagnosis due to screening tests often leads to a complete cure. Colorectal cancer starts in the large intestine, also known as the colon. Nearly all colon cancers begin as noncancerous, or benign, polyps, some of which may slowly develop into cancer. Screening can detect these polyps and early cancers. Polyps can be removed years before cancer even has a chance to develop. Your doctor can use two types of tools to screen for cancer. The first type is a stool test. Polyps in the colon and small cancers can bleed tiny amounts of blood that you can't see with the naked eye. The most common method to test for the presence of blood is the fecal occult blood test or FOBT. This test checks your stool for small amounts of blood that you may not be able to see. Two other stool tests are the fecal immunochemical test and the stool DNA test. The second type of screening tests involve looking at the lining of the colon. One of these tests is a sigmoidoscopy exam. This test uses a flexible scope to look at the lower portion of your colon. But, because it looks only at the last one-third of the large intestine, it may miss some cancers. So this test is done along with a stool test. A colonoscopy is similar to sigmoidoscopy, but it can see the entire colon. For this test, your doctor will give you instructions for cleansing your bowel. This is called bowel preparation. During the colonoscopy, you’ll receive medicine to make you relaxed and sleepy. Another test your doctor may recommend is a virtual colonoscopy, also called a CT colonography. This test uses a CAT scan and computer software to create a 3-D image of your large intestine. Beginning at age 45, all men and women should have a screening test for colon cancer. Screening options for people with average risk for colon cancer include visual based exams. These could be a colonoscopy every 10 years starting at age 45 or a virtual colonoscopy every 5 years. A Flexible sigmoidoscopy every 5 years or a Flexible sigmoidoscopy every 10 years plus stool testing with FIT done every year. Screening options also include stool based tests. People with average risk should have an FOBT or FIT every year. A colonoscopy is needed if the results are positive, or a Stool DNA test every 1 to 3 years. A colonoscopy is needed if the results are positive. People with certain risk factors for colon cancer may need screening at a younger age, or they may need screening more often. Such people include those with a family history of colon cancer, those with a history of previous colon cancer or polyps, or people with a history of ulcerative colitis or Crohn disease. The death rate for colon cancer has dropped in the past 15 years and this may be due to increased awareness and colon screening. In general, early diagnosis is much more likely to lead to a complete cure.
There are several ways to screen for colon cancer.
- 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 (gFOBT). Two other tests are called the fecal immunochemical test (FIT) and stool DNA test (sDNA).
- 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.
- 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.
- 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 the most thorough but also has the highest risk. Talk to your provider about which test is right for you.
All adults should have a colon cancer screening test starting at age 45.
Screening options for people with an average risk for colon cancer:
- Colonoscopy every 10 years starting at age 45
- gFOBT or FIT every year (colonoscopy is needed if results are positive)
- sDNA-FIT every 1 to 3 years (colonoscopy is needed if results are positive)
- Flexible sigmoidoscopy every 5 years or every 10 years plus stool testing with FIT done every year
- CT colonography (virtual colonoscopy) every 5 years
SCREENING FOR HIGHER-RISK PEOPLE
People with certain risk factors for colon cancer may need earlier (before age 45) 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.
Garber JJ, Chung DC. Colonic polyps and polyposis syndromes. In: Feldman M, Friedman LS, Brandt LJ, eds. Sleisenger and Fordtran's Gastrointestinal and Liver Disease. 11th ed. Philadelphia, PA: Elsevier; 2021:chap 126.
National Cancer Institute website. Colorectal cancer screening (PDQ) – health professional version.
Rex DK, Boland CR, Dominitz JA, et al. Colorectal cancer screening: recommendations for physicians and patients from the U.S. Multi-Society Task Force on Colorectal Cancer. Am J Gastroenterol. 2017;112(7):1016-1030. PMID: 28555630
US Preventive Services Task Force, Davidson KW, Barry MJ, et al. Screening for Colorectal Cancer: US Preventive Services Task Force Recommendation Statement [published correction appears in JAMA. 2021 Aug 24;326(8):773]. JAMA. 2021;325(19):1965-1977. PMID: 34003218
Wolf AMD, Fontham ETH, Church TR, et al. Colorectal cancer screening for average-risk adults: 2018 guideline update from the American Cancer Society. CA Cancer J Clin. 2018;68(4):250-281. PMID: 29846947
Last reviewed on: 7/30/2022
Reviewed by: Michael M. Phillips, MD, Emeritus Professor of Medicine, The George Washington University School of Medicine, Washington, DC. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.