CT colonography is effective in the right hands, complements conventional optical colonoscopy well, and appeals to consumers, according to a study of about 1100 patients at the University of Wisconsin, Madison.
After demonstrating the effectiveness of particular virtual colonoscopy methods in a peer-reviewed study, the university's virtual colonoscopy program became one of the first in the country to win reimbursement from managed care companies.
Results from the first year of experience on a reimbursable basis, through April 2005, will be published by Dr. Perry J. Pickhardt and colleagues in the November issue of Radiology.
Software improvements in the virtual colonography product used in the study, the Viatronix V3D-Colon, helped improve performance and speed compared with previously published studies, according to the researchers.
For the most part, reading a study took no longer than 10 minutes. The positive predictive value per patient for lesions 6 mm or larger on CT colonography was 93.8% versus 58.5% for an earlier trial done at the same institution. No serious complications occurred.
Changes in protocol also helped. One disadvantage of CT colonography is that patients still need to undergo optical colonoscopy if treatment is required following detection. Both procedures require bowel preparation, which can be uncomfortable for patients.
In the Wisconsin study, scheduling allowed patients to undergo both procedures in the same day if necessary, with just one bout of bowel preparation. Patients underwent CT colonography between 7 a.m. and 10 a.m. If lesions larger than or equal to 10 mm were detected, the patients could go on to the conventional procedure in the same day whenever possible. When 6 to 9-mm polyps were found, the choice of going on to either optical colonoscopy or to short-term follow-up with CT colonography was left to the patient.
In the initial study group of 1192 patients, optical colonoscopy was incomplete in about 7%, and these were excluded from the trial. Of the remaining 1110 patients, 43 had large polyps, and all of these cases were referred for conventional colonoscopy. Of 77 with medium-sized polyps, 40% chose optical colonoscopy, and the rest opted for short-term follow-up with CT colonography.
Most patients (86%) who needed follow-up optical colonoscopy were able to get the procedure done on the same day. Overall, only 10% of the study group required optical colonoscopy, and in these patients, 90% of lesions were confirmed with the conventional procedure.
The authors stressed that the positive results were linked to the particular methods used by experienced professionals, which were proven to be effective and reported previously in the literature (Pickhardt PJ et al. NEJM 2003;349:2191-2200).
They also reported that the number of patients undergoing screening doubled from the start of 2004 to 2005, possibly due to increased demand spurred by the introduction of insurance coverage. Patients have taken to the virtual colonoscopy service, even without any advertising initiatives, according to the study.
It is estimated that currently only 40% of people who could benefit from colorectal screening actually have the procedure done, resulting in unnecessarily high mortality rates for preventable types of cancer. An increase in utilization could have a positive impact on mortality rates.
CT colonography will not replace optical colonoscopy, which is still needed to treat polyps that are found on virtual studies, the researchers said.
For more information from the Diagnostic Imaging archives:
CT colonography tools advance in clinical use
CT colonography promotion belies gold standard preference of imagers
PET/CT colonography could provide 'all-in one' staging
