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.
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 (FOBT). 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 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.
Colon cancer is one of the leading causes of cancer-related deaths in the United States. The good news is that early diagnosis through preventive screening 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, which slowly develop into cancer. Screening can detect these polyps and early cancers. The great thing is that we can remove polyps years before cancer even has a chance to develop! Your doctor can use several tools to screen for cancer. The first step is a stool test. This test checks your bowel movements for blood that you may not even be able to see in your stool. 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 is called the fecal occult blood test. A second method is called 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. That's why this test is usually done along with a stool test. A colonoscopy is similar to sigmoidoscopy, but it can see the entire colon. That's why we usually do colonoscopies over sigmoidoscopies nowadays. You'll usually be mildly sedated during this test. Occasionally, your doctor may recommend, as an alternative, a double-contrast barium enema--which is a special x-ray of the large intestine, or a virtual colonoscopy, which uses a CAT scan and computer software to create a 3-D image of your large intestine. So, who should be screened for colon cancer? Well, beginning at age 50, men and women should have a screening test. People with an average risk of colon cancer should have a colonoscopy every 10 years, a double-contrast barium enema every 5 years, or a fecal occult blood test every year. Additional options are sigmoidoscopy every 5 to 10 years. People with certain risk factors for colon cancer may need screening before age 50, or more frequent testing. Such people include those with a family history of colon cancer, African-Americans, those with a history of previous colon cancer or polyps, or folks with a history of ulcerative colitis or Crohn's disease, which are both chronic inflammatory bowel diseases. 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 can lead to a complete cure.
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 website. Final recommendation statement. Colorectal cancer screening.
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: 7/15/2020
Reviewed by: Michael M. Phillips, MD, Clinical Professor of Medicine, The George Washington University School of Medicine, Washington, DC. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.