New Technique Shows Promise for Detecting Colon Cancer
Nov. 10, 1999 (Seattle) -- Using computer-generated images, doctors can spot
early signs of colon cancer without subjecting their patients to an
uncomfortable procedure, according to a study in the Nov. 11 edition of
TheNew England Journal of Medicine. But experts say the new
technique still has flaws and is several years away from widespread use.
The study looked at a procedure called virtual colonoscopy. It's done using
a noninvasive technique called computed tomography, or CT scanning, to capture
a series of high-quality X-ray images of the large intestine. The images are
fed into a computer, which uses them to create a three-dimensional
representation of the entire colon. Using a computer equipped with special
software, a doctor can examine this 'virtual colon' for polyps, small growths
that can lead to cancer.
Virtual colonoscopy is designed as an alternative to conventional
colonoscopy, in which a doctor uses a long, flexible tube to examine the
intestine. Researchers say the procedure is uncomfortable, and people
undergoing it usually have to be sedated. Also, they say, there is a small risk
that the tube will puncture the wall of the intestine during the examination.
As a result, the procedure is usually reserved for patients who are thought to
be at high risk for colon cancer.
The study of virtual colonoscopy was done by a team at Boston University.
They had doctors examine 100 patients at high risk of colon cancer using both
the virtual and conventional techniques on each individual.
Both techniques found three cancerous growths. But conventional colonoscopy
proved slightly better than its virtual counterpart at detecting polyps. Most
of the polyps missed by virtual colonoscopy were small, and none of them proved
to be cancerous.
Joseph Ferrucci, MD, an author of the study and chairman of radiology at
Boston University Medical School, tells WebMD that virtual colonoscopy still
needs some refinement. "In skilled hands it's already an effective
technique," he says, "But we need more studies before it can be widely
John Bond, MD, chief of gastroenterology at the Minneapolis VA Medical
Center, tells WebMD that virtual colonoscopy still has some significant flaws.
One is that in order to get good images of the intestine, doctors must inflate
it with air. "Many patients find that uncomfortable," he says.
Bond, the author of an editorial that accompanied the Boston University
study, says a more significant problem with virtual colonoscopy is that it
still isn't accurate enough. "It still misses an appreciable number of
fairly large polyps that could be dangerous," he says.
But Bond, like Ferrucci, believes the new procedure has a bright future. He
says, "I have no doubt that with time it will improve so that it can
compete with conventional colonoscopy."