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Cheaper, Easier Virtual Colonoscopy Could Boost Detection
04.23.07, 12:00 AM ET
MONDAY, April 23 (HealthDay News) -- A cutting-edge technology called "virtual colonoscopy" promises fewer complications and better cost-effectiveness than traditional colonoscopy, researchers report.
These technologies have been compared before, but the current analysis relies on the notion that identifying and removing polyps smaller than 6 millimeters won't do much to reduce colorectal cancer cases.
"Because there's virtually no risk associated with having such small polyps, 90 percent of folks don't need an invasive and expensive colonoscopy to screen for colon cancer," explained lead researcher Dr. Perry J. Pickhardt, an associate professor in the school of medicine and public health and radiologist at the University of Wisconsin in Madison.
"So, here it was easy to show that virtual colonoscopy is a very effective way to filter out these people and hone in on those who really need the more invasive procedure," he said.
Pickhardt is not suggesting that virtual colonoscopies replace traditional optical screening. But non-invasive screening might up the number of people who decide to undergo screening, he said.
"We need to encourage more folks to get screened, period," he said. "We're not trying to take away from the screening already in place. It's a personal choice. Some people prefer the colonoscopy route compared to virtual colonoscopy, and that's fine. Just so long as you do one or the other."
Pickhardt and his colleagues discussed their findings in the June 1 issue of the journal Cancer.
According to the American Cancer Society (ACS), colorectal cancer is the third most common cancer in the United States among both men and women.
People over the age of 50, smokers, African-Americans, Jews of Eastern European descent, those with a personal or family history of the disease, or those with a history of polyps or bowel disease are at an increased risk for colon or rectal cancer.
The ACS estimates that more than 112,000 Americans will be diagnosed with colon cancer this year. Colorectal cancers will also take the lives of about 52,000 Americans.
The disease is highly treatable if caught early, however.
Virtual colonoscopy involves a combination of sophisticated X-rays and CT scans of the abdomen after it has been pumped with air. A two- and three-dimensional computer model of the gastrointestinal tract is then generated, potentially revealing cancerous and precancerous lesions. If dangerous lesions are spotted, a second, more invasive procedure is required.
Unlike traditional colonoscopy, the virtual method is faster, involves no sedation, no post-procedure recovery, and no risk of invasive complications such as abdominal bleeding or life-threatening bowel perforation.
However, the ACS has not yet backed this option as a proven screening method, citing the need for further research.
Instead, the group suggests other screening methods, including blood stool tests; a barium enema combined with X-rays; a flexible sigmoidoscopy (involving the insertion of a two-foot-long optical tube through the rectum to examine the lower colon) and traditional optical colonoscopy, which involves the insertion of a longer lighted tube to examine the entire colon.
All people over 50 are encouraged to undergo a regular colonoscopy once every 10 years, or either a barium enema or a flexible sigmoidoscopy (with or without a yearly blood test) once every five years. The ACS does not deem a digital rectal exam to be a sufficient means of screening.
To compare some of these options, Pickhardt and his colleagues developed a mathematical model involving 100,000 patients with an average risk for colorectal cancer. They noted that 75 percent of the American population is subject to such risk.
In the computer simulation, all of these "patients" (over the age of 50) were screened for colon cancer once every decade for three decades, using either a standard colonoscopy, a flexible sigmoidoscopy, a virtual colonoscopy, or a combination thereof.
Polyp searches were based on one of two thresholds: those measuring 6 millimeters in diameter and up, and lesions of any size.
The model indicated that 2,940 patients would ultimately go on to develop colorectal cancer.
The simulation also revealed that flexible sigmoidoscopy screenings reduced the rate of cancer by just over 31 percent, while traditional colonoscopy reduced the rate by just over 40 percent.
Virtual colonoscopies were only slightly less efficient than the traditional method -- achieving an almost 38 percent reduction when polyps of all sizes were considered. The prevention rate dropped slightly, to 36.5 percent, when screenings focused only on polyps 6 millimeters and up.
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作者:admin@医学,生命科学 2010-10-21 17:11
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