Colorectal Cancer Screening

By Puneet Singh Cheema, MD, HealthEast Cancer Care Medical Director

The American Cancer Society believes that preventing colorectal cancer, and not just diagnosing it early, should be the major reason for getting tested. Regular colorectal cancer screening (via endoscopy) is one of the most powerful means of preventing colorectal cancer. Finding and removing polyps keeps some people from getting colorectal cancer. Tests that have the best chance of finding both polyps and cancer are preferred if these tests are available to you and you are willing to have them.

When to start screening

People who have no identified risk factors (other than age) should begin regular screening at age 50. Those who have a family history or other risk factors for colorectal polyps or cancer, such as inflammatory bowel disease, should talk with their doctor about starting screening at a younger age or getting screened at more frequent intervals.

People with a strong family history, especially those who have had colorectal cancer before age 50, should be referred for genetic counseling and consideration of genetic testing.

If you are at average risk

People who are at an average risk should follow these guidelines.

Tests used to find polyps:

flexible sigmoidoscopy - every 5 years*
colonoscopy - every 10 years
double contrast barium enema - every 5 years*
CT colonography (virtual colonoscopy) - every 5 years*

Tests that mainly find cancer:

fecal occult blood test (FOBT) - every year*,**
fecal immunochemical test (FIT) - every year*,**
stool DNA test (sDNA) - interval uncertain*

* Stool DNA tests are looking for blood in the stool. These tests look for certain abnormal sections of DNA (genetic material) from cancer or polyp cells. Colorectal cancer cells often contain DNA mutations (changes) in certain genes such as APC, K-ras, and p53. Cells from colorectal cancers or polyps with these mutations are often shed into the stool, where tests may be able to detect them.

This is a newer test, and the best length of time to go between tests is not yet clear. This test is also much more expensive than other forms of stool testing. This test is not invasive and doesn't require any special preparation. But as with other stool tests, if the results are positive,* a colonoscopy is required to investigate further. People having this test will receive a kit with detailed instructions from their doctor's office or clinic on how to collect the specimen. Always follow the instructions on your kit.

This test requires an entire stool sample. It is obtained using a special container and sent in an ice pack in a shipping box for the testing. The specimen must be shipped to the lab within 24 hours of having the bowel movement.

**For FOBT or FIT used as a screening test, the take-home multiple sample method should be used. A FOBT or FIT done during a digital rectal exam in the doctor's office is not adequate for screening.

In a digital rectal examination (DRE), a doctor examines your rectum with a lubricated, gloved finger. Although a DRE is often included as part of a routine physical exam, it is not recommended as a stand-alone test for colorectal cancer. This simple test, which is not usually painful, can detect masses in the anal canal or lower rectum. By itself, however, it is not a very sensitive test for detecting colorectal cancer due to its limited reach.

If you are at increased or high risk

If you are at an increased risk or higher than average risk of colorectal cancer, you should begin colorectal cancer screening earlier, be screened more often and use colonoscopy as your screening method.

The following conditions place you at higher than average risk:

A personal history of colorectal cancer or adenomatous polyps
A personal history of inflammatory bowel disease (ulcerative colitis or Crohn's disease)
A strong family history of colorectal cancer or polyps
A known family history of hereditary colorectal cancer syndromes such as familial adenomatous polyposis (FAP) or hereditary non-polyposis colon cancer (HNPCC)

Next page: Treatment Options for Colorectal Cancer