A "virtual" colonoscopy catches pre-cancerous growths as reliably as the conventional physical exam, offering a less invasive way to avoid one of the top cancer killers, researchers reported Monday.
The largest study to directly compare the new test to traditional colonoscopies found the scan spots worrisome polyps at least as accurately, and perhaps even more so, indicating it would provide a powerful tool to reduce the toll from the common malignancy.
"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. It's an exciting time. We could save countless lives."
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. But if caught early, colon cancer is highly curable. As a result, doctors recommend regular colonoscopies. Many people avoid the procedure, however. It involves snaking 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. Only about 37 percent of colon cancers are diagnosed before they have progressed.
The virtual colonoscopy allows people to avoid having the physical exam, which carries a small but not insignificant small risk of piercing the colon. People undergoing both procedures still have to go through the unpleasant task of purging their digestive systems the night before, but the virtual test requires no anesthesia or sedation. That means they don't need to take time off work or have someone accompany them to the test to drive them home.
"There's no recovery time. It doesn't require intravenous sedation or analgesia. Patients can basically go back to work right after they have the virtual colonoscopy," Pickhardt said.
A virtual colonoscopy involves a CT scan of the abdominal area. 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 individual 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 to 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.
"It might seem like a minor variation. But it's a paradigm shift," Pickhardt said in a telephone interview.
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 in a paper being published in Thursday's issue of the New England Journal of Medicine. The paper was released early to coincide with a presentation at the annual meeting of the Radiological Society of North America in Chicago.
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 only 88.2 percent and 89.5 percent of such polyps. Virtual colonoscopy caught two malignant polyps, including one that the conventional test missed.
Pickhardt said he hoped the findings would convince other radiologists to start using the same technique, and insurance companies to start paying for it. The test costs between $600 and $1,000, compared to 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."
Pickhardt and his colleagues have already convinced insurers in the Madison area to pay for it and are offering it to the general public.
"It's an exciting time. This may sound a little dramatic, but to pretty much eradicate colon cancer would be the ultimate goal of widespread screening," he said.
In an editorial accompanying the results in the medical journal, J. Thomas Lamont, chief of gastroenterology at the Beth Israel Deaconness Medical Center in Boston, called the findings "impressive" and said that if the results are confirmed virtual colonoscopy would be "ready for prime-time."
"I think what we're seeing here is the evolution of a technique and technology that now places it next to regular colonoscopy," Lamont added in a telephone interview. "I'd like to see a big multicenter study to see if doctors in regular practice can come up with the same results."
Douglas K. Rex, director of endoscopies at the Indiana University Hospital in Indianapolis and president of the American College of Gastroenterology, agreed that the results were encouraging, but also cautioned that the findings needed to be confirmed.
"I think it should be verified. One study ... does not change everything. We've previously seen a very wide range of results. But the bottom line is we should be encouraged. These are good results."
