Researchers boost `virtual' colonoscopy
The colonoscopy, a much dreaded medical exam, now has a high-tech competitor that can detect tumors inside the intestines with equal accuracy but without the sedation, health risks, or pain of the standard test.
According to a new study, the "virtual colonoscopy," which probes intestines using computerized X-ray images, catches a few more suspicious colon growths than a traditional colonoscopy, in which physicians snake tubelike cameras several feet into patients' bowels.
"It is convincing data. . . . The two tests appear equivalent," said Dr. J. Thomas LaMont, chief of gastroenterology at Beth Israel Deaconess Medical Center.
The virtual tests cost between $600 and $1,000 and are not yet widely available. They are now used chiefly in hospitals to examine patients with bowel conditions that make standard colonoscopies difficult.
Standard colonoscopies, which cost about the same, are almost universally covered by insurance. So far insurers have considered data supporting the accuracy of virtual colonoscopies to be lacking.
"What [the insurers] wanted is proof that it's efficacious," said LaMont. "This study might be it."
In the study, released yesterday by the New England Journal of Medicine, 1,223 adults underwent colon cancer screening with both procedures.
The study was the first large-scale head-to-head comparison of the screening abilities of the two tests.
The virtual colonoscopy caught 93.8 percent of colon growths smaller than 10 millimeters across -- about the width of a marble -- and the standard test caught 87.5 percent. The virtual test discovered two cancerous tumors among the patients, where the standard test missed one of them.
In addition, the virtual colonoscopy, which scans the entire abdominal region, found five cancers outside the colon, as well as several problems in blood vessels, kidneys, and gallbladders.
If a problem in the bowel is discovered, however, patients would have to have a standard colonoscopy procedure to have the growth removed. One advantage of the standard colonoscopy exam is that the doctor can usually remove any growths discovered during the test itself.
"Virtual colonoscopies are definitely an option," said LaMont, who was not involved in the study but who wrote an editorial accompanying today's report.
The study's authors, many treating patients at US military hospitals, wrote that the virtual test "compares favorably" with traditional colonoscopy.
The study's lead author, Dr. Perry J. Pickhardt of the University of Wisconsin Medical School, said in an interview yesterday, "There's now a preponderance of evidence that this is effective. . . . Coverage by third-party insurers should be the next step." Pickhardt predicted insurers would begin covering the procedure within a year, and said it was likely that the approval of the virtual test by Medicare, the federal government health insurance for the elderly, would spur other private insurers to cover it.
Standard colonoscopies, recommended for those turning 55, are widely dreaded for their physical discomfort and inconvenience, as well as their small but significant risk for complications. The procedures take up to two hours. The patient is sedated as the camera passes through the rectum and the bowels.
Patients often take up to an hour to recover, and cannot drive the same day. There is a risk of bleeding and tears, which happens in about 3 in 1,000 cases, according to studies.
Virtual colonoscopies involve the same pretest preparations as colonoscopies, including maintaining a liquid diet for up to three days and taking strong laxatives the night before the procedure. But the procedure itself lasts about 15 minutes; no sedation is involved. As air is lightly pumped into the rectum, multiple CT scans, from different angles, are taken of the abdominal region. The scans are merged to create a three-dimensional image of the area.
Physicians typically spend about 20 minutes analyzing test results. Patients can walk out and go home.
"With regular colonoscopy . . . you have to wake up in the hospital and have someone take you home in a car," said LaMont. "With virtual colonoscopy, all you get is an air enema."
Virtual colonoscopy evolved over the last decade, as physicians and cancer specialists experimented with powerful CT scanning devices to detect potentially malignant growths in hard-to-reach regions of the body. Since the technique was first developed, scanning techniques continue to progress: Researchers in this latest study used a slight variation on previous techniques that they said provided the clearest three-dimensional images to date.
Colon cancer strikes 135,000 Americans annually, killing 57,000. Only lung cancer kills more.
Physicians recommend that all Americans get screened for colon cancer at age 55, then again a decade later. But it is estimated that only a third of Americans in that age group have been screened. Many aren't even aware of the test, and others are turned off by its reputation as painful and intrusive.
LaMont is enthusiastic about the power of virtual colonoscopies but would settle for more people getting either test.
"This is a disease we could eliminate if everyone had one of these tests," he said.
Raja Mishra can be reached at rmishra@globe.com.
