X-ray alternative to colon test found effective

Method cheaper, could get more to screen for cancer

By Mike Stobbe,
ATLANTA, 21 sept 2008 - A long-awaited federal study of an X-ray alternative to the dreaded colonoscopy confirms its effectiveness at spotting most cancers, although it was far from perfect.
Medicare is already considering paying for this cheaper, less invasive option that could induce more people to get screened for colon cancer. Some scientists believe the new method may boost the 50 percent screening rate for a cancer that is the nation's second-biggest killer.
"We're talking about for the first time really screening the population," said Dr. Carl Jaffe, an imaging expert at the National Cancer Institute who was not involved in the research.
In the new study, the largest of its kind, the so-called virtual colonoscopy identified 9 out of 10 people who had cancers and large growths seen by regular colonoscopies.
But there were flaws, too. Among them: Radiologists sometimes misread the X-ray, spotting polyps that weren't there.
That led to unnecessary follow-up testing.
The X-ray test's greatest value may be in showing who really needs a regular colonoscopy. The X-ray was better at ruling out cancer than it was at detecting it, suggests the report in today's New England Journal of Medicine.
Colorectal cancer will claim about 50,000 lives this year. The point of screening, widely recommended at age 50, is to find growths before they turn cancerous.
The gold standard is colonoscopy, in which a long, thin tube equipped with a small video camera is snaked through the large intestine to view the lining. Any growth can be removed during the procedure.
It requires sedation and a missed day of work, not to mention preparation that uses pills or liquids to clean out the bowel.
The study focused on CT colonography, also known as virtual colonoscopy. It's a super X-ray of the colon that is quicker, cheaper, and easier on the patient than traditional colonoscopies.
However, it, too requires the bowel clean-out and has a potentially serious drawback - radiation.
Colonoscopies cost up to $3,000. The X-ray test costs $300 to $800; most insurers don't cover it so far, but Medicare is considering it.
Insurers probably will weigh the new study heavily in their coverage decisions, said Dr. Durado Brooks, who oversees colorectal and prostate cancer programs at the American Cancer Society.
Preliminary, unpublished data from the new study already helped persuade the cancer society and others to put out guidelines in March that added virtual colonoscopy and a stool DNA test to the recommended arsenal of screenings for colon cancer, Brooks said.
In the new study, both the standard colonoscopy and the X-ray test were given to 2,531 people at 15 US medical centers.
The scans showed large growths in about 1 in 6 people, although some were false alarms not confirmed by colonoscopy.
Of the patients with growths verified by colonoscopy, 90 percent were flagged through the X-ray scans.
But only 1 in 4 of those patients diagnosed with a growth actually had one, noted Dr. Robert Fletcher, a retired Harvard Medical School professor who wrote an editorial accompanying the study. He is a paid consultant for a company that makes a DNA screening test for colon cancer.