CT Virtual Colonoscopy for Colorectal Neoplasia

Abstract & Commentary

Synopsis: Unlike previous studies that demonstrated superiority of optical colonoscopy, this trial found that the 2 procedures were similar for detection of clinically significant lesions.

Source: Pickhardt P, et al. N Engl J Med. 2003;349(23): 2191-2200.

This multicenter study compared results of initial virtual colonoscopy with a 3-dimensional computerized tomographic (CT) approach with subsequent standard video colonoscopy. In this study, 1233 patients were evaluable (others had incomplete colonoscopy or CT failure or poor preparation). Pneumocolon for CT colonoscopy was patient controlled. For polyps 8 mm or larger, virtual colonoscopy was more than 92% accurate with > 99% accuracy for larger polyps (and quite acceptable levels of specificity). All centers had comparable results for virtual colonoscopy.

Optical colonoscopy was actually a bit less sensitive than radiography. Two malignant polyps were found with virtual colonoscopy, one having been initially missed on optical colon examination. Time in x-ray was 14.1 minutes vs 31.5 minutes in the endoscopy suite (mean total time including recovery was 95.9 minutes).

Overall, 54.3% of patients rated virtual colonoscopy as more uncomfortable, but more patients still related an overall preference for virtual colonoscopy. Pickhardt and colleagues recommend virtual colonoscopy for screening of low-risk or average-risk individuals and suggest that finding a polyp of 8 mm or larger on this exam should mandate immediate optical colonoscopy and polypectomy. In this study, 86.5% of the patients screened would not have required optical colonoscopy if the 8 mm level of polyp size had been selected.

Comment by Malcolm Robinson, MD, FACP, FACG

Virtual colonoscopy has finally arrived as a viable option for colon screening. As an accompanying New England Journal of Medicine editorial points out, colon screening has been recommended for all average-risk adults beginning at age 50, a formidable medical undertaking with a high cost. Could virtual colonoscopy replace a significant fraction of currently recommended optical colonoscopies? The answer is unclear, but there are a number of potential disadvantages to the radiographic approach. First, unlike optical colonoscopy that is potentially simultaneously diagnostic and therapeutic, virtual colonoscopy provides no therapeutic benefit. Patients who need a follow-up standard colonoscopy with polypectomy almost certainly will require a second aggressive coloncleansing regimen since immediate endoscopy for positive findings will seldom be available. Although the ultimate commercial cost for virtual colonoscopy is uncertain, it is likely to be quite high. Overall expense of a protocol that includes both modalities may be unacceptably high. Most medical insurance currently doesn’t cover virtual colonoscopy. Admittedly, as a gastroenterologist, I am biased toward optical colonoscopy. As a patient, I am quite sure that I would opt for endoscopic examination of my colon. However, if the availability of virtual colonoscopy led to increased numbers of patients willing to undergo colon screening, I and most other gastroenterologists would have to welcome this new procedure to the overall diagnostic armamentarium.

Dr. Robinson, Medical Director, Oklahoma Foundation for Digestive Research; Clinical Professor of Medicine, University of Oklahoma College of Medicine Oklahoma City, OK, is Associate Editor of Internal Medicine Alert.