Virtual colonoscopy a less invasive cancer screener

Our Review Summary

On September 18, 2008, the long anticipated results of the American College of Radiology Imaging Network (ACRIN) CT Colonography trial were published in the New England Journal of Medicine. This trial represented the largest, multicenter trial evaluating CT colonography as a screening method for colon cancer in asymptomatic adults. The hope was that this study would clarify whether CT colonography could be considered a recommended routine screening method on par with colonoscopy and other established tests. In the study, CT colonography identified 9 out of 10 large polyps as seen on colonoscopy, but performed less well for smaller lesions. The American Cancer Society and other organizations moved to endorse CT colonography, but the US Preventive Services Task Force (USPSTF) did not, citing several drawbacks to the test, including the need for follow-ups on extracolonic findings (suspicious findings found outside the colon on the CT scan), radiation exposure and concerns about operator variability in the interpretation of the CT scans.

The story quotes multiple experts but attained no balance because all of those quoted were fans of the approach.  The evidence-based perspective of the USPSTF was not reflected in the story. 

The story does not adequately describe the availability of virtual colonoscopy, which may be limited to large or academic medical centers. Nor does the study adequately describe the testing alternatives. The story mentions colonoscopy but does not mention other alternatives to CT colonography, such as fecal-occult blood testing or flexible sigmoidoscopy as colon cancer screening methods.

Although the story mentions radiation exposure (underplaying the controversy over this) and missed polyps as potential harms of CT colonography, it does not mention additional harms such as operator variability in the interpretation of the CT scans and extracolonic findings. Also, not only does the story overstate the cost of traditional colonoscopy (it is much less than $3000), it should not have gone so far as to speculate that HHS would rule in favor of covering virtual colonoscopy, especially given the recent USPSTF recommendations.

Furthermore, the story does not adequately describe the strength of the available evidence to support virtual colonoscopy as a routine colon cancer screening method. The story mentions the recent study but does not fully describe the findings of the study, such as the fact that the test performed poorly in finding small polyps and that suspicious findings were found outside of the colon in almost 1 in 5 study participants. These findings required additional testing and follow up evaluation. In addition, the story mentions that the American Cancer Society and the American College of Oncology endorse the test, but does not mention that the USPSTF does not recommend routine use of the test based on their independent evidence review.

The story also exaggerates the novelty of CT colonography by referring to it as "science fiction" and likening it to "Star Wars" and a "video game". Clearly, CT technology – even with 3D reconstruction – is not new but the idea that it can be used for colon cancer screening is relatively new.

Finally, although the story does not exaggerrate the prevalence or mortality of colon cancer, the story crosses the line into disease mongering in its description of polyps, calling them a "monster… sprouting inside a patient’s large intenstine like a mushroom". More importantly, though, it falsely claims that most polyps develop into cancer in 10 years. This kind of misstatement does a disservice to the reader in obscuring the clinical reality with fear mongering.