In the United States, colorectal cancer (CRC) is the third leading cause of cancer, after breast and lung cancer.
CRC almost always develops from precancerous polyps (abnormal growths in the colon or rectum). Screening tests can find precancerous polyps so they can be removed before they turn into cancer. Screening tests can also find CRC early, when treatment works best.
A screening test is used to look for a disease when a person has no symptoms. (When symptoms are present, diagnostic tests are used to find out the cause.)
Regular screening begins at age 45. The U.S. Preventative Services Task Force (USPSF) recommends adults age 45 to 75 be screened. For adults age 76 to 85, the Task Force recommends asking their doctor for screening recommendations.
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Several screening tests can be used to find polyps and/or CRC (see Table 1 below). There is no single “best test” for any person. Each test has advantages and disadvantages. Talk to a virtual doctor about which test may be best for you and how often to be tested. Testing modality depends on personal preference, individual medical conditions, the likelihood of testing, and the resources available for testing and follow-up.
Table 1. Screening Tests for CRC
| Test Name | Description | Testing Frequency |
| Stool TestsGuaiac-based fecal occult blood test (FOBT) | Uses the chemical guaiac to detect blood in stool. Test provided by health care provider. At home, use a stick or brush to obtain a small amount of stool. Return the test kit to doctor or lab, where stool samples checked for presence of blood. | Once a year. |
| Fecal immunochemical test (FIT) | Uses antibodies to detect blood in stool. | Once a year. |
| FIT-DNA test (or stool DNA test) | Combines the FIT test with a test that detects altered DNA in the stool. This test requires an entire bowel movement be collected and sent to a lab, where it is checked for cancer cells. | Once every 3 years. |
| Flexible Sigmoidoscopy | During this test, the doctor inserts a short, thin, flexible, lighted tube into the rectum through the sigmoid colon (lower 1/3 of colon). The doctor checks for polyps or cancer there. | Every 5 years, or every 10 years with a FIT every year. |
| Colonoscopy | Similar test to flexible sigmoidoscopy, except the doctor uses a longer, thin, flexible, lighted tube to check for abnormalities inside the rectum and entire colon. During the procedure, the doctor can find and remove most polyps and some cancers. Colonoscopy is also used as a follow-up test if anything unusual is found during one of the other screening tests. | Every 10 years (for people who do not have an increased risk of colon cancer). |
| CT Colonoscopy (Virtual Colonoscopy) | Computed tomography (CT) colonography, also called virtual colonoscopy, uses X-rays and computers to produce images of the entire colon. These are displayed on a computer screen for the doctor to analyze. | Every 5 years. |
The screening testing frequencies above are general guidelines and may be different for you if you have certain risk factors for CRC, such as a family history of CRC or detection of high-risk lesion. Testing is generally more frequent for patients who are high risk. Your doctor will help you decide the optimal screening interval.
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