Colorectal Cancer Overview

+ -Text Size

Early Detection, Diagnosis, and Staging TOPICS

How is colorectal cancer found?

Colorectal cancer screening tests

Screening tests are used to look for disease in people who do not have any symptoms. In many cases, these tests can find colorectal cancers at an early stage and greatly improve treatment outcomes. Screening tests can also help prevent some cancers by allowing doctors to find and remove polyps that might become cancer. Screening tests for colorectal cancer include:

  • Fecal occult blood test (FOBT) and fecal immunochemical test (FIT): Samples of stool (feces) are checked for blood, which might be a sign of a polyp or cancer.
  • 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.

FOBT and FIT mainly find cancer, but can find some polyps.

Sigmoidoscopy, colonoscopy, double contrast barium enema, and CT colonography are good at finding cancer and polyps. Polyps found before they become cancer can be removed, so these tests may prevent colorectal cancer. This is why these tests are preferred if they are available and you are willing to have them.

For more details about these tests, please see Colorectal Cancer Early Detection.

Preventing colorectal cancer or finding it early

Colon cancer begins with a growth (a polyp) that is not yet cancer. Testing can help your doctor tell whether there is a problem, and some tests can find polyps before they become cancer. Most people who have polyps removed never get colon cancer. If colon cancer is found early, you have a good chance of beating it with treatment. Testing can find it early.

The American Cancer Society believes that preventing colorectal cancer (not just finding it early) should be a major reason for getting tested. Finding and removing polyps keeps some people from getting colorectal cancer. Tests that have the best chance of finding both polyps and cancer should be your first choice if these tests are available to you and you are willing to have them.

Doctors will take into account a number of things when they talk to you about the tests you should have, how often you should have them, and when you should begin testing. These factors include whether you are at average, increased, or high risk for colorectal cancer. If you are at increased or high risk, the type of test used and how often it is done will depend on whether you have had polyps, cancer, or certain other diseases, as well as your family history.

In general, both men and women at average risk of colorectal cancer should begin screening tests at age 50. But you should talk with your doctor about your own health and your family history so that you can choose the best screening plan for you.

For more detailed information about the American Cancer Society's recommendations for screening, please see our document Colorectal Cancer Early Detection. This document also has information about insurance coverage for colorectal cancer screening.


Last Medical Review: 08/15/2013
Last Revised: 01/31/2014