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Why is it important to find colorectal cancer early?

Screening is the process of looking for cancer or pre-cancer in people who have no symptoms of the disease. Regular screening can often find colorectal cancer early, when it is most likely to be curable.

In many people, screening can also prevent colorectal cancer by finding and removing polyps before they have the chance to turn into cancer.

What tests are used to screen for colorectal cancer?

Tests used to screen for colorectal cancer include:

  • Guaiac-based fecal occult blood test (gFOBT) and fecal immunochemical test (FIT): Samples of stool (feces) are checked for blood, which might be a sign of a polyp or cancer.
  • Stool DNA test: A sample of stool is checked for certain abnormal sections of DNA (genetic material) from cancer or polyp cells.
  • Sigmoidoscopy: A flexible, lighted tube is put into the rectum and lower colon to check for polyps and cancer.
  • Colonoscopy: A longer, flexible tube is used to look at the entire colon and rectum.
  • Double-contrast barium enema: This is an x-ray test of the colon and rectum.
  • CT colonography (virtual colonoscopy): This is a type of CT scan of the colon and rectum.

gFOBT, FIT, and stool DNA testing mainly find cancer, but can find some polyps.

Sigmoidoscopy, colonoscopy, double contrast barium enema, and CT colonography are good at finding both cancer and polyps. These tests are preferred if they are available and you are willing to have them.

For most adults, the American Cancer Society recommends starting screening with one of these tests at age 50. Some people at higher risk for colorectal cancer might need to start screening earlier.

For more about these tests and their use in finding colorectal cancer early, see Colorectal Cancer Prevention and Early Detection.


Last Medical Review: 10/15/2015
Last Revised: 01/20/2016