A noninvasive scan can find the most dangerous, precancerous polyps with about the same accuracy as the dreaded colonoscopy – and without the risk of bowel perforation, according to an influential study at UCSD and 14 other research centers.
“We now have another tool to catch these polyps early, and one that's less risky and easier on the patient,” said Dr. Giovanna Casola, a professor of radiology at the University of California San Diego and an author of the report.
|
COLON CANCER
 Second-leading cancer killer and the third-most commonly diagnosed cancer in the United States.
Up to 60 percent of people 50 and older fail to have routine exams to look for signs of colon cancer.
The earlier significant polyps are removed, the lower a person's risk of developing the disease.
Too few servings of fruits and vegetables or a high-fat diet with red meat, fried foods and high-fat dairy products may increase the risk of colon cancer.
|
|
“We can save lives, and that's the bottom line,” she said. “This gives patients a choice.”
The study is published in today's edition of the New England Journal of Medicine, whose prestige may prompt insurance companies and Medicare to pay for the procedure, called CT colonography or virtual colonoscopy.
Medicare and private insurers now cover CT colonography only for people who are frail or have intestinal conditions that preclude colonoscopy, said a spokesman for the American Association of Health Plans.
The Mayo Clinic in Scottsdale, Ariz., led the colonography study, which was funded by the National Institutes of Health and the American College of Radiology Imaging Network. Some contributing researchers have financial ties to companies that make CT colonography equipment or software.
Public health organizations recommend that people be screened for colon cancer starting at age 50, and then every 10 years afterward. Testing should be more frequent if polyps are found.
Yet up to 60 percent of people in the 50-and-older category fail to get the regular checkups, according to the American College of Radiology. About 50,000 people in the United States die of colon cancer each year, usually because screening came too late.
Part of the reluctance comes from the undignified process of taking laxatives up to a day before a colonoscopy to cleanse the bowel. People must still do that with CT colonography. But the scan eliminates anesthesia, which requires patients to take up to a day off work to recover from grogginess.
The CT test also would expose people to a small amount of radiation.
Radiologists expect to find significant polyps in about 17 percent of patients, who would then need traditional colonoscopy to have them removed. But the remaining 83 percent would avoid the risk of potentially fatal bowel perforation, which occurs in about two per 1,000 people who undergo colonoscopy.
In the new study, CT colonography identified 90 percent of the people with polyps measuring 10 millimeters, about the size of a marble, or greater. These lesions are most likely to be cancerous.
Missing 10 percent of the large polyps is not good, the researchers said, but the noninvasive test is ultimately beneficial because it will persuade more people to undergo screening for colon cancer.
CT colonography also found smaller polyps, but with less accuracy. For example, the test found 78 percent of polyps 6 millimeters or bigger.
While costs for CT colonography and colonoscopy vary depending on the region of the country, the range is up to $3,000 for colonoscopy and up to $1,000 for colonography.
Radiologists said the new study validates CT colonography as an important screening tool, but gastroenterologists, the doctors who perform colonoscopies, expressed more measured enthusiasm.
While the CT scan may encourage more people to undergo colon checkups, adults at higher risk for colon cancer – those who have had polyps or have a family history of the disease – “should go right to the gold standard, which is colonoscopy,” said Dr. John Petrini, president of the American Society for Gastrointestinal Endoscopy.
High-risk people can't afford to have a potentially cancerous polyp missed, he added. Also, if they have to undergo a colonoscopy, they would save time and discomfort by enduring the bowel cleansing only once.
To be safe, Petrini said, gastroenterologists typically remove all polyps during colonoscopy.
“This trial's message is not a one-size-fits-all,” he said. “If someone is 45 and is not in a high-risk group but is just nervous about getting cancer, (CT colonography) might be OK. But they need to know there is some risk from exposure to X-rays.”
Above all, he said, patients need to consult their doctors about which test is right for them.
Beyond finding polyps, CT colonography sometimes spots abnormalities outside the colon that may or may not be clinically significant. These discoveries may provoke further testing and invasive procedures that are unnecessary.
“We have to fine-tune which lesions are significant. But the upside is that we may pick up problems, like kidney masses or abdominal aneurysms or masses at the bottom of the lung,” said Casola, the UCSD researcher.
The colonography study enrolled more than 2,500 people – about 75 through UCSD – who didn't have any symptoms of bowel disease. Most of the participants had a low risk of colon cancer.
All performed the normal bowel-cleansing preparations. Then they underwent CT colonography and a few hours later had traditional colonoscopy.
The American College of Radiology recommends that gastroenterologists and radiologists work together so people who need both procedures can have them done in the same day.
But Petrini said that is unlikely to happen soon.
“You can't expect doctors to sit there and say we're going to leave gaps in our schedule in case someone comes in” requiring removal of polyps, he said.
Cheryl Clark: (619) 542-4573; cheryl.clark@uniontrib.com
