Less invasive virtual colonoscopy gets high marks for efficacy for average-risk people.
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Highlights
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What is virtual colonoscopy?
Virtual colonoscopy is computed tomographic (CT) colonography. It is an advanced type of CT (or CAT) scan that, like traditional colonoscopy, closely examines the inside of both the rectum and the colon. Unlike traditional colonoscopy, however, virtual colonography is not invasive.
Traditional colonoscopy uses a colonoscope, a flexible, lighted, camera-equipped tube that is inserted into the rectum. Virtual colonography uses x-rays to create 2- and 3-dimensional images, which the doctor can use to view the colon and rectum for polyps and other possible pre-cancerous changes.
Recent Study Results Positive
American Cancer Society Colorectal Cancer Screening Recommendations
The American Cancer Society recommends that men and women at average risk of colon cancer get screened regularly beginning at age 50. People at higher risk may need to begin screening at a younger age.
There are many screening tests available. Some are able to find precancerous polyps, as well as cancer. These tests are typically more invasive, but they are preferred if you are willing to have them. Other screening methods can detect cancer, but are less likely to find polyps. Talk to your doctor about which of these screening tests is right for you.
Tests that can find both polyps and cancer:
- 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 primarily find cancer:
- Fecal occult blood test (FOBT) every year*,**
- Fecal immunochemical test (FIT) every year*,**
- Stool DNA test (sDNA), interval uncertain*
* A colonoscopy should be done if results are positive
** 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.
According to a recent clinical trial, virtual colonography is about as effective as traditional colonoscopy when it comes to finding colorectal cancer and large polyps.
The study, called the National CT Colonography Trial, was the largest study to date comparing the two screening tests. It included 2,500 participants. Each person in the study underwent CT colonography, followed by a standard colonoscopy on the same day.
CT colonography correctly found 90% of polyps measuring 10 millimeters or more in diameter (this size polyp is more likely to be pre-cancerous than a smaller one). Although the test was less sensitive for smaller lesions – those measuring 6 to 9 millimeters, it still found 65% of them.
A cautionary note: While CT colonography is a good screening test for those at average risk for colorectal cancer, it isn't recommended for people at high risk. For those at high risk, traditional colonoscopy is still the gold standard for finding colorectal cancer early.
The Pros and Cons of CT Colonography
The Pros:
- CT colonography may be a welcome option for those who are uncomfortable with the invasive nature of traditional colonoscopy and therefore tend to put it off or avoid it altogether.
- CT colonography carries a much smaller risk of perforating the colon wall than traditional colonoscopy.
- CT colonography does not require sedation, so the patient doesn’t have to take a day off work or find a ride to and from the procedure.
- CT colonography only takes about 10 minutes.
- CT colonography is typically less expensive than traditional colonoscopy.
The Cons:
- CT colonography requires the same amount of bowel preparation – such as liquid diets and strong laxatives on the day before the test – as traditional colonoscopy.
- CT colonography does not allow doctors to remove any polyps or biopsy any suspicious areas seen during the test. That means if anything abnormal is found, the patient will still need to come back for a traditional colonoscopy (and that means another bowel preparation).
- CT colonography may miss some smaller, possibly pre-cancerous polyps that would likely be caught and removed during a traditional colonoscopy.
- CT colonography does expose the patient to a low level of radiation. This risk is hard to assess because it is not yet known if this might cause problems over many years of regular screening.
Colorectal cancer, commonly called colon cancer, is the third most common cancer diagnosed among both men and women in the United States, and the second leading cause of cancer death. Although rates of this disease have been decreasing in recent years, they could be even lower if all people who should be screened actually got screened.
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