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Virtual Colonoscopy Is Less Invasive But Less Reliable

March 14, 2005

Studies suggest the technique still needs refinement

HealthDayNews — Colonoscopy is the potentially life-saving procedure that everyone over 50 knows they should get, but one that few want to endure.

It utilizes a tiny camera inside a slender tube that’s inserted through the rectum. This lets the physician look for early signs of cancer inside the entire large intestine, from the rectum all the way through the colon to the lower end of the small intestine.

But it requires the use of powerful laxatives and sometimes days of liquid diet. And that’s only part of the regimen. The patient must also be sedated for a full colonoscopy, so he or she can lose a day or more between the preparation and the procedure itself.

With March designated National Colorectal Cancer Awareness Month, doctors are urging people 50 and older who are at average risk for developing the disease to undergo a colonoscopy to ensure they stay cancer-free. Doctors emphasize the need for colonoscopy because colorectal cancer is the one form of cancer in men and women that is totally preventable through early screenings.

But because of the complicating factors associated with colonoscopy, many people risk their lives by avoiding the test.

“They’re afraid of the procedure,” said Dr. David Alberts, director of the University of Arizona Cancer Center. “They can’t fit it into their schedule. It’s a very sad event when we see these men and women in their 60s with metastatic colon cancer never having had a colonoscopy.”

Researchers are working to perfect a less-inconvenient substitute procedure called virtual colonoscopy.

In virtual colonoscopy, a CT scan of the abdomen is used to create a computer-generated model of a person’s colon and the organs surrounding it. Doctors review the two- or three-dimensional model to look for obvious abnormalities, such as cancerous or pre-cancerous lesions.

However, recent research has found virtual colonoscopies do not detect colon cancer as efficiently or accurately as a standard colonoscopy.

For the time being, a traditional colonoscopy remains the best method for detecting and preventing colon and rectal cancer, which will cause approximately 56,290 deaths in 2005, according to the American Cancer Society.

“Usually what I tell people is that a traditional colonoscopy is the gold standard,” said Eden Stotsky, a colon cancer survivor and health educator for the Johns Hopkins Cancer Center in Baltimore.

Through the traditional test, physicians can find and remove precancerous lesions on the spot. “If you find the polyp and remove it, your chances of getting colon cancer reduces significantly,” Stotsky said.

The American Cancer Society estimates that about 104,950 new cases of colon cancer and 40,340 new cases of rectal cancer will be diagnosed in 2005.

Doctors are holding out hope that virtual colonoscopy eventually will provide a more convenient alternative, particularly for younger people undergoing routine exams. Patients still have to endure unpleasant test preparation involving laxatives, but don’t have to be sedated for the procedure.

“Because there are no sedatives, there is no down time,” Alberts said. “You can come in and have the procedure, then drive home or go to work.”

Virtual colonoscopy is ideal for patients who react poorly to sedatives or who do not like invasive procedures, according to experts.

“It seems to promise that it has the absence of significant invasiveness,” said Dr. Bernard Levin, vice president of cancer prevention at the University of Texas MD Anderson Cancer Center in Houston. “There’s no tube involved, no sedation needed and is very much quicker.”

However, a study performed at Oregon Health & Science University found that virtual colonoscopy was associated with more cancer deaths and procedure-related deaths than standard colonoscopy.

According to the research, there were 66 more colon cancer deaths per 100,000 patients who had virtual colonoscopy, compared with standard colonoscopy. The findings were presented at the annual meeting of the American College of Gastroenterology in November.

That research was supported by another study published in the Jan. 1, 2005, issue of The Lancet. This study found that traditional colonoscopy was much more accurate in detecting small lesions.

For example, traditional colonoscopy found 99 percent of polyps between 6 millimeters and 9 millimeters, while virtual colonoscopy found only 64 percent of polyps that size.

“There is still a gap between the high promise and the delivery,” Levin said. “I would say we’re two to five years away from knowing how virtual colonoscopy can be optimized for screening and follow-up.”

Alberts said the big problem is that virtual colonoscopy is a complex procedure and most radiologists don’t have the proper training. He said that in facilities with highly trained staff, virtual colonoscopy has proven nearly as accurate as traditional colonoscopy.

“It’s a very outstanding technology, but the technology has outstripped the ability of the human,” Alberts said. “I think that will change over time, but you can’t be absolutely sure when you go to a virtual colonoscopy who the radiologist is or how much training he or she has had, and that is a problem.”

Another drawback is that if a polyp is found during a virtual colonoscopy, the patient will have to undergo preparation and come back for a traditional colonoscopy to remove the lesion.

Levin envisions a day when clinics have facilities for both virtual and traditional colonoscopy, side-by-side.

“That way, you can go back and have a conventional colonoscopy the same day without having to cleanse again,” he said. “That would be the most efficient way this could be done.”

More information

To learn more about colonoscopies, visit the National Digestive Diseases Information Clearinghouse.




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