Study applauds colon-cancer test

By The Associated Press and The Washington Post

E-mail this article Print this article Search archive

CHICAGO — A procedure that lets doctors find abnormal growths in the colon through three-dimensional, computer-generated images is at least as accurate and is less invasive than conventional colonoscopy, researchers reported yesterday.

Researchers hope the results will encourage screenings among people who avoid conventional colonoscopy because of the discomfort associated with it.

Colon cancer strikes an estimated 105,500 Americans each year and kills more than 57,000, making it the second leading cancer killer after lung cancer.

If caught early, colon cancer is highly curable. That's why the American Cancer Society recommends that adults over 50 get a colonoscopy every 10 years. However, fewer than half of those who should get screened do so, the society estimates.

"Colon cancer is a largely preventable disease — we just have to get people through the door to get screened," said Perry Pickhardt, an associate professor of radiology at the University of Wisconsin Medical School in Madison, who tested the new approach. "This could help do that. ... We could save countless lives."

The study was presented yesterday in Chicago at the annual meeting of the Radiological Society of North America.

In a conventional colonoscopy, patients take laxatives to cleanse their bowels 24 hours before the procedure. They are sedated before the doctor snakes a long tube with a small camera attached to the end into the colon to look for polyps, which can go on to become cancerous.

"A lot of people that I talk with — even other physicians — are afraid of the 'long snake,' " said the study's co-author, Lt. Col. J. Richard Choi.

Patients undergoing a virtual colonoscopy still have to purge their digestive systems the night before, but the virtual test requires no sedation.

That means patients don't need to take time off work or have someone drive them home.

In a virtual colonoscopy, a small rectal catheter is inserted and a CT scan of the abdominal area is performed. CT, which stands for computed tomography, uses special X-ray equipment to obtain a series of cross-sectional pictures of the inside of the body from different angles. A computer program assembles the images into what essentially looks like a film moving through the entire length of the colon.

Doctors can watch the images on a computer screen, looking for signs of a polyp. If they find one, the patient would immediately be referred for a standard colonoscopy and possibly a biopsy.

In recent years, many radiologists have begun using the technique to screen for polyps. But studies comparing the test with standard colonoscopy have produced mixed results, with the high-tech approach often appearing more likely to miss polyps.

For the new study, Pickhardt and his colleagues used what they consider to be a superior technique that, among other things, produces images in three dimensions instead of just two.

When he was at the Naval Medical Center in Bethesda, Md., Pickhardt and colleagues at three medical centers performed both conventional and virtual colonoscopies on 1,233 adults, most of whom were at average risk for polyps.

Overall, the virtual colonoscopy detected more than 90 percent of all significant polyps, performing slightly better than conventional colonoscopy and much better than previous studies of the virtual technique, the researchers reported.

For example, virtual colonoscopy detected 92.2 percent of polyps 10 millimeters in size and 92.6 percent of those at least 8 millimeters in size. Conventional colonoscopy detected 88.2 percent and 89.5 percent of such polyps.

Pickhardt said he hoped the findings would persuade other radiologists to start using the technique, and insurance companies to start paying for it. The test costs between $600 and $1,000, compared with about $650 for a conventional colonoscopy.

"Once this becomes reimbursable by Medicare and other payers, I think you'll see a pretty rapid adoption," Pickhardt said. "I think it will happen on a pretty rapid basis."

Copyright © 2003 The Seattle Times Company