New research suggests that CT or virtual colonography is as accurate as conventional optical colonoscopy in detecting
large adenomas and malignancies.  The new study was prompted by mixed results from three previous trials, in
which two found that CT colonography gave only mediocre results,
whereas it was as good as colonoscopy in the third.

The largest ever comparative study examined 2,531 asymptomatic patients 50 or
older undergoing routine colon cancer screening, the sensitivity of CT
colonography for lesions of 10 mm or larger was 0.90 (95% CI 0.84 to
0.96) on a per-patient basis.  The data was published in the Sept. 18
issue of the
New England Journal of Medicine.

For lesions at least 6 mm in diameter, the sensitivity was 0.78 (95% CI 0.71 to 0.85). Specificities at the 10-mm and 6-mm thresholds were 0.86 (95% CI 0.82 to 0.90) and 0.88 (95% CI 0.84 to 0.92), respectively. These
findings translated to positive and negative predictive values at the
10-mm threshold of 0.23 (SE 0.02) and 0.99 (SE 0.01), respectively.

The current study used
standard optical colonoscopy as the reference, even though its
sensitivity and specificity is less than perfect but represents the current standard of care.

In an accompanying editorial, Robert Fletcher of Harvard
Medical School, said physicians and patients should be cautious about
substituting CT colonography for colonoscopy.  He noted the positive
predictive value for CT colonography in the new study was only about
25%, meaning that a significant number of patients without actual
polyps will end up undergoing colonoscopy anyway.

However, Dr. Johnson said
performance was just one consideration that physicians and patients
should take into account when deciding on which screening procedure to
use.  The others are patient acceptability, safety, and cost.  CT colonography was clearly better in these categories, he noted.

Both technologies require bowel
prep, but patients don't require sedation for colonography and the
procedure is considerably faster.  Risk of complications is also "very low" in comparison with colonoscopy and the cost is expected to about half of colonoscopy.

Overall, CT or virtual colonoscopy looks to be an attractive, cheaper and less invasive option compared to traditional colonoscopies.

What would you rather do?

{UPDATE: The CMS recently rejected virtual colonoscopies for Medicare patients, although elderly patients are the ones most likely to benefit from less invasive virtual colonoscopy.}

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