CT Colonography Equal to Optical Colonoscopy, says Study

CT colonography is a better screening test than optical colonoscopy (OC), according to a new study published in the MayRadiology print issue. Using meta-analysis of studies done over a 15 year period, authors found that the sensitivity of CT colonography for colorectal cancer detection was 96.1 percent, compared with 94.7 percent for OC.

Authors noted that their study supported the clinical equivalence of CTC and OC for screening invasive cancers. They felt the CTC was mature enough to be seen as a universal procedure.

Aside from the sensitivity rates being roughly equal, there are other reasons that the CTC can be better for screening, including cost and the minimal invasiveness. One potential downside, however, is that CTC exposes the patient to radiation, though lead author Perry J. Pickhardt, MD, a professor of radiology at the University of Wisconsin School of Medicine doesn’t think the amount is concerning. “CTC is a low-dose exam applied to adult patients,” he said. “There are no meaningful implications related to the radiation exposure.”

The meta-analysis ultimately included 49 studies covering 11,551 patients, done from January 1994 (the year that CT colonography was first mentioned), through 2009. All the CTC studies were for screening, to diagnose colorectal polyps and cancer, and all positive results were proven histologically. Six studies, encompassing 42 percent of the participants, focused on asymptomatic patients typical in a screening setting. The remaining 43 studies included symptomatic patients and/or a disease-enriched population.

Authors note the low prevalence of invasive colon cancer in screenings, citing a cumulative 3.6 percent rate from the meta-analysis. A total of 414 colorectal cancers were found in the studies, including 20 in the screening group (less than a 0.5 percent prevalence rate) and 394 in the disease-enriched group (almost a 6 percent prevalence rate).

As for the cost, Pickhardt says that using CTC is less expensive. “Our work has shown that CTC is considerably more cost-effective as a primary screening test compared with colonoscopy.”

One reported reason that patients are less likely to get a colonscopy is because the evacuatory and uncomfortable nature of the bowel preparation. Plus, OC requires the use of some anesthesia or medication for patient comfort. With CTC, those issues are diminished, according to Pickhardt. “CTC is much less invasive, requires no IV for sedation or pain medication, and requires no recovery time,” said Pickhardt, adding that patients don’t need a driver to take them home. “In addition, our low-volume bowel prep is much better tolerated than the typical colonoscopy preps in use.”