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What’s Up With Virtual Colonoscopy?

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The future of virtual colonoscopy seems … well, let’s just say the images are fuzzy.

Just last month, a study published in The Journal of the National Cancer Institute concluded that computed tomographic colonography (CTC), also known as virtual colonoscopy, was “not cost-effective when reimbursed at the same rate as colonoscopy.”

Now comes an Italian study, published online tomorrow in the World Journal of Gastroenterology, suggesting that CTC should replace colonoscopy as the first option for colorectal cancer screening. “In this setting,” the study concludes, “CTC has clear advantages, such as accuracy, safety and subject acceptance.” The study did recommend further research regarding the screening rates that would result from adopting CTC over colonoscopy and “the real cost and benefits derived from a CTC screening program.”

The researchers analyzed three large recent studies and a number of smaller studies. They concluded that CTC is highly accurate, with the only trouble spot being too many false positives for polyps smaller than 10 mm. On the other hand, they say, there were very few false negatives, and “this is extremely important in order to reassure negative patients about the significance of the examination.”

The researchers note that “colonoscopy … suffers from a very low participation rate,” with potential patients complaining about the required bowel preparation, embarrassment, and fear of discomfort. CTC is perceived to be more comfortable, but as to whether its widespread use would increase screening rates, “we need data resulting from real screening experience.”

The researchers flatly state: “CTC is a safe test, definitely safer than colonoscopy.” CTC, they say, has a much lower perforation rate. Concerning CTC’s radiation exposure and the accompanying risk of cancer, they say, “The risk is theoretical because there are still many uncertainties with regard to the true effects of ionizing radiation at low doses, such as those used in diagnostic radiology.” They say that the mean exposure of a CTC screening exam has recently been calculated to be only about twice the normal yearly background radiation exposure in the United States, and that screening CTCs would take place only once every five years.

Frankly, the researchers dance around the cost issue, saying, “Cost analysis is a very difficult task, especially in the absence of real data and based only on mathematical models.” They do suggest that the cost-benefit analysis should take into account the ancillary ability of CTC to detect “previously unknown life-threatening diseases” such as abdominal aortic aneurysm and renal cancer.

So where does that leave us? Waiting for more research, of course. Also, probably, waiting for costs to come down. Still, if CTC can be sold to the public as more comfortable than colonoscopy, and if that leads to significantly higher screening rates, then it probably does have a bright future.

Related seminar: Imaging Advances: Abdominal, Thoracic, Skeletal (brand new release)

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