The Laxative-Free 'Virtual Colonoscopy'
Eliminating the Need for Bowel Prep Could Spur More People to Get Screened for Colon Cancer
Electronic 'Cleansing' continued...
The researchers found that the laxative-free CT colonography accurately identified 9 out of 10 patients with precancerous polyps 10 millimeters or larger. Generally, about 15% of virtual colonoscopies detect an abnormal growth that must be removed through a conventional colonoscopy, Zalis says.
"Accepted practice" in colon cancer screening is that precancerous polyps that are 6 millimeters or larger should be removed, the scientists write. However, they add, about 91% of the most dangerous polyps are at least 10 millimeters in size.
People in Zalis' study said they preferred the comfort and preparation for the virtual colonoscopy over that for the conventional colonoscopy.
A Dutch study published in January had similar results. Researchers randomly divided people ages 50-75 into two groups: One was invited to have a conventional colonoscopy, the other a laxative-free virtual colonoscopy. While colonoscopy picked up more advanced abnormal growths, a higher percentage of people invited to have CT colonography agreed to be screened.
Virtual Colonoscopy Uncommon
Although virtual colonoscopy eliminates another off-putting aspect of conventional colonoscopy -- the need to insert a long, thin tube called a colonoscope through the entire length of the colon -- relatively few Americans have opted for the procedure.
In 2010, only about 1 in 100 Americans aged 50-75 reported ever having a virtual colonoscopy, according to CDC and National Cancer Institute data published this month.
In 2008, the American Cancer Society endorsed CT colonography every five years as an acceptable colon screening method. But Medicare doesn't routinely cover the procedure, Zalis says. "Appropriately, there's a high bar placed on screening."
Private insurers tend to follow Medicare's lead, so virtual colonoscopy is not widely reimbursed. As a result, Zalis says, relatively few doctors have learned how to do it.
Zalis says Massachusetts General is not yet promoting laxative-free CT colonography because his findings need to be confirmed by other researchers. However, he says, if a patient who's never been screened asks about having a laxative-free colonography, "we'd definitely do the exam."
The findings of Zalis' study are "intriguing," says gastroenterologist Samir Gupta, MD, an assistant professor of internal medicine at the University of Texas Southwestern Medical Center in Dallas.