Colorectal Cancer Screening, Part 2

by National Cancer Institute

(Page 2 of 2)

5. How can people and their health care providers decide which colorectal cancer screening test(s) to use and how often to be screened?

Several major organizations, including the U.S. Preventive Services Task Force (a group of experts convened by the U.S. Public Health Service), the American Cancer Society, and professional societies, have developed guidelines for colorectal cancer screening. Although some details of their recommendations vary regarding which screening tests to use and how often to be screened, all of these organizations support screening for colorectal cancer.

People should talk with their health care provider about when to begin screening for colorectal cancer, what tests to have, the benefits and risks of each test, and how often to schedule appointments.

The decision to have a certain test will take into account several factors:

• Person's age, medical history, family history, and general health;
• Accuracy of the test;
• Risks associated with the test;
• Preparation required before the test;
• Sedation necessary during the test;
• Follow-up care after the test;
• Convenience of the test; and
• Cost and insurance coverage of the test.

The following table outlines some of the advantages and disadvantages of the colorectal cancer screening tests described in this fact sheet.

Fecal Occult Blood Test (FOBT)

Advantages

• No preparation of the colon is necessary.
• Samples can be collected at home.
• Cost is low compared to other colorectal cancer screening tests.
• FOBT does not cause bleeding or tears in the lining of the colon.

Disadvantages

• This test fails to detect most polyps and some cancers.
• False positive results are possible. ("False positive" means the test suggests an abnormality when none is present.)
• Dietary and other limitations, such as increasing fiber intake and avoiding meat, certain vegetables, vitamin C, iron, and aspirin, are often recommended for several days before the test.
• Additional procedures, such as colonoscopy, may be necessary if the test indicates an abnormality.

Sigmoidoscopy

Advantages

• The test is usually quick, with few complications.
• Discomfort is minimal.
• In some cases, the doctor may be able to perform a biopsy (the removal of tissue for examination under a microscope by a pathologist) and remove polyps during the test, if necessary.
• Less extensive preparation of the colon is necessary with this test than for a colonoscopy.

Disadvantages

• This test allows the doctor to view only the rectum and the lower part of the colon. Any polyps in the upper part of the colon will be missed.
• There is a very small risk of bleeding or tears in the lining of the colon.
• Additional procedures, such as colonoscopy, may be necessary if the test indicates an abnormality.

Colonoscopy

Advantages

• This test allows the doctor to view the rectum and the entire colon.
• The doctor can perform a biopsy and remove polyps during the test, if necessary.

Disadvantages

• The test may not detect all small polyps and cancers, but it is the most sensitive test currently available.
• Thorough preparation of the colon is necessary before the test.
• Sedation is usually needed.
• Although uncommon, complications such as bleeding and/or tears in the lining of the colon can occur.

Double Contrast Barium Enema(DCBE)

Advantages

• This test usually allows the doctor to view the rectum and the entire colon.
• Complications are rare.
• No sedation is necessary.

Disadvantages

• The test may not detect some small polyps and cancers.
• Thorough preparation of the colon is necessary before the test.
• False positive results are possible.
• The doctor cannot perform a biopsy or remove polyps during the test.
• Additional procedures are necessary if the test indicates an abnormality.

Digital Rectal Exam (DRE)

Advantages

• Often part of a routine physical examination.
• No preparation of the colon is necessary.
• The test is usually quick and painless.

Disadvantages

• The test can detect abnormalities only in the lower part of the rectum.
• Additional procedures are necessary if the test indicates an abnormality.

6. Do insurance companies pay for colorectal cancer screening?

Insurance coverage varies. People should check with their health insurance provider to determine their colorectal cancer screening benefits. Medicare covers several colorectal cancer screening tests for its beneficiaries.

7. What happens if a colorectal cancer screening test shows an abnormality?

If screening tests find an abnormality, the health care provider will perform a physical exam and evaluate the person's personal and family medical history. Additional diagnostic tests may be ordered. These may include x-rays of the gastrointestinal tract, sigmoidoscopy, or most often, colonoscopy (see Question 4). The health care provider may also order a blood test called a CEA assay to measure carcinoembryonic antigen, a protein that is sometimes present in higher levels in patients with colorectal cancer.

If an abnormal area is found during a colonoscopy, a biopsy is performed to determine if cancer is present. If an abnormal area is found during a sigmoidoscopy, a biopsy may be performed during the test, and a colonoscopy may be recommended.

8. Are new tests under study for colorectal cancer screening?

New tests for colorectal cancer screening are under study. For example, virtual colonoscopy (also called computed tomographic colonography) is a procedure that uses special x-ray equipment to produce pictures of the colon. A computer then assembles these pictures into detailed images that can show polyps and other abnormalities. Because it is less invasive and does not require sedation, virtual colonoscopy may cause less discomfort and take less time than conventional colonoscopy. However, as with conventional colonoscopy and DCBE, thorough preparation of the colon is necessary before the test.

Unlike conventional colonoscopy, it is not possible to remove polyps or perform a biopsy during virtual colonoscopy. An additional procedure, such as conventional colonoscopy, is needed if the virtual procedure finds a potential problem. Clinical trials (research studies with people) are under way to compare the advantages and disadvantages of virtual colonoscopy with those of other colorectal cancer screening tests.

Genetic testing of stool samples is also under study as a possible way to screen for colorectal cancer. The lining of the colon is constantly shedding cells into the stool. Testing stool samples for genetic alterations that occur in colorectal cancer cells may help doctors find evidence of cancer or precancerous polyps. Research conducted thus far has shown that this test can detect colorectal cancer in people already diagnosed with this disease by other means. However, more studies are needed to determine whether the test can detect colorectal cancer or precancerous polyps in people who do not have symptoms.

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