FRIDAY, April 2, 2004 (HealthDayNews) -- Colorectal cancer is one of the most preventable of all cancers.
Yet it's also one of the most "under-screened" malignancies.
Virtually all malignant colorectal tumors develop from polyps, which are easily identified and removed if a person just gets the proper screening. Unfortunately, "if" appears to be the operative word here.
"One of the major reasons why we still have 140,000 cases a year and 55,000 deaths, making it the number one solid-tumor killer after tobacco-related malignancies, is that our screening rates are very low," says Dr. Thomas Weber, an associate professor of surgery at Albert Einstein College of Medicine and Montefiore Medical Center in New York City.
"With these low rates, we have a major problem," Weber adds. "We need some alternatives to try and boost those rates."
One promising new alternative is the "virtual colonoscopy," which made headlines after Today show co-host Katie Couric underwent the procedure several years ago on television.
And University of Wisconsin researchers reported in a recent issue of the New England Journal of Medicine that virtual colonoscopy compares favorably to the current "gold standard" of conventional colonoscopy.
For now, conventional colonoscopy remains the standard screening tool. It involves inserting a long, flexible, lighted tube called a colonoscope into the rectum, then guiding it up through the intestine. The tube snaps pictures of your bowels and then relays them out to the doctor performing the procedure.
A virtual colonoscopy, also called a CT colonography, is an imaging procedure that involves taking an X-ray of the rectum and colon from the outside. There's no tube involved. "It uses computer-based software to enhance and make two- and sometime three-dimensional images of a patient's colon," Weber says.
There are decided advantages to a virtual colonoscopy. "It's quicker, only a couple of minutes, and there's no sedation needed," says Dr. David Beck, chairman of the department of colon and rectal surgery at the Ochsner Clinic Foundation in New Orleans. And because there's no sedation, the patient can drive him or herself home.
Also, a conventional colonoscopy carries some risks, chiefly perforation of the intestine, although this is relatively rare. "One or two people per every 1,000 may have an untoward event in terms of the colonoscopy," Weber says. "The death rates are very low, less than two per 10,000."
On the other hand, one of the major drawbacks that patients complain about with a traditional colonoscopy -- having to drink copious amounts of liquids to empty out the intestine -- is still an issue with a virtual colonoscopy.
"Right now, you have to take the same kind of prep and you also have to put some air in the colon to make it easier to take pictures so there's some distension," Beck points out. The preparation can also dehydrate a person, adding to potential risk.
A conventional colonoscopy offers several important advantages over a virtual colonoscopy. It is, in a manner of speaking, a form of "one-stop-shopping." If something suspicious is identified, it can be removed immediately during the procedure.
"We know that 25 percent of all average-risk Americans who present at age 50 for their first screening colonoscopy will have polyps," Weber says. A virtual colonoscopy can only identify the presence of something; it cannot remove it for further investigation. If something shows up, the person would then have to go through a traditional colonoscopy as well.
Also, Beck says, Medicare and most insurance companies will pay for a colonoscopy, but won't pay for a virtual colonoscopy.
There is also limited availability of the virtual version. "There are a lot of CT scanners around and very few have the new software to do this kind of test," Beck says. "Most of the CT scans are pretty booked up."
Finally, there's the issue of human error with a virtual colonoscopy. You need to make sure you have a radiologist skilled in reading this type of image, which can take longer than with a conventional colonoscopy. "A very, very important issue is that the results are operator-dependent," Weber says.
That said, there's still a place for the virtual colonoscopy in the health-care world.
"Some people have a tumor in their lower rectum where they can't get the scope past so they can't see the whole colon," Beck says. "For that person, this is going to be very helpful."
Also, a virtual colonoscopy is likely to be safer for people who have had their blood thinned for problems such as heart disease, Beck adds. And it will be more palatable for those who just can't stomach the idea of an invasive colonoscopy, Weber says.
"I think [the virtual colonoscopy] is going to be complementary," Beck says. "There are over 50 million people [in the United States] over the age of 50. If every gastroenterologist and colorectal surgeon scoped five days a week, they still couldn't do them all. I think [virtual colonoscopy] is going to have a role but what that role exactly is going to be is still being worked on."
More information
The National Institute of Diabetes and Digestive and Kidney Diseases has more on conventional colonoscopies and on virtual colonoscopies.
