Virtual screening: Colonoscopy without the hassle

Colorectal cancer (CRC) is the second most common cause of cancer deaths in the U.S. (after lung cancer). And, while these cancers are largely preventable if caught early, many people dodge the unpleasant colonoscopy screenings that are crucial for diagnosis and early treatment. However, a procedure known as virtual colonoscopy, or a CT colonography, is a non-invasive diagnostic procedure, and a large study just published in Lancet Oncology has found that the method persuaded more people to undergo CRC screening.

CT colonography has been around since 1994, yet reservations about its accuracy have prevented this procedure from being more widely used. However, the Lancet study, conducted by researchers from the Academic Medical Center in Amsterdam, suggests that the lower sensitivity of virtual colonoscopy is balanced by the greater number of people who are willing to undergo the virtual procedure as opposed to a standard colonoscopy. Unlike a standard colonoscopy, the CT scan requires neither the dreaded bowel cleansing preparation, nor any sedation or anaesthesia for the procedure.

In a randomized, population-based trial, nearly 6,000 people aged 50 to 75 were invited to undergo a primary CRC screening. Of this group, half were offered standard colonoscopy and half were offered CT colonography. While only 22 percent of the participants offered standard colonoscopy accepted the screening, 34 percent of those who were offered the virtual procedure agreed to be screened.

Thus, although the relative chance of finding a precancerous lesion (a polyp) or a cancer was significantly higher in those undergoing a standard colonoscopy, the fact that 1.5 times as many people were actually screened via CT colonography meant that the total number of potentially life-threatening lesions detected were about equally distributed between the two methods. However, any abnormality detected via virtual colonoscopy must still be followed up with a standard colonoscopy, suggesting that the newer method will eventually be most widely used in concert with the conventional procedure.

While ACSH s Dr. Elizabeth Whelan points out that conventional colonoscopy is not only more accurate but also therapeutic, she sees the clear advantage in being able to screen more people with the virtual procedure. As ACSH s Dr. Gilbert Ross points out, Colorectal cancer is preventable. If everyone had a colonoscopy every five or 10 years, the death rate from colorectal cancer would drop dramatically.