Data published in the Journal of the National Cancer Institute assert that computed tomographic colonography (CTC) (virtual colonoscopy) is cost-effective only when priced lower than conventional colonoscopy or if it attracts a large unscreened population. The limitations of the study include weaknesses inherent to computer models, limited consideration as to the risks and costs associated with exposure to radiation during CTC, and uncertainty concerning the increased costs attributed to extracolonic diseases that become evident with CTC.

CTC is a minimally invasive imaging technique that simulates the view seen during conventional colonoscopy. The goal of CTC is to detect precancerous and cancerous lesions that can subsequently be removed at an early stage (by conventional colonoscopy) when treatment is likely to be most effective.

The study was performed in response to a request by the Centers for Medicare & Medicaid Services (CMS) to support approval for reimbursement. Three simulated computer models were used to measure outcomes and costs associated with CTC performed every 5 years compared with:

• No screening
• Annual fecal occult blood test (FOBT)
• Flexible sigmoidoscopy every 5 years
• Flexible sigmoidoscopy every 5 years in combination with the annual FOBT
• Colonoscopy every 10 years (current reference standard)

Compared with colonoscopy screening every 10 years, the number of life-years gained from virtual colonoscopy every 5 years was slightly decreased if adherence to screening was 100%. If virtual colonoscopy was reimbursed at $488—approximately the same rate as colonoscopy screening—the associated lifetime cost of virtual colonoscopy surpassed that of colonoscopy screening. However, if relative adherence to virtual colonoscopy screening was 25% higher compared with other tests, it could be cost-effective if reimbursed at $488 per scan. With 100% adherence, CTC would be cost-effective at between $108 and $205 per scan.

In May 2009, CMS announced that based, in part, on this evidence, it would not cover CTC as a screening test for colorectal cancer. An accompanying editorial confirms that CTC often finds abnormalities outside the colon—in such areas as the kidneys or adrenal glands—that lead to further tests and procedures but are not likely to prolong life.  However, the editorialist suggests that traditional colonoscopy often leads to removal of small polyps unnecessarily, sometimes leading to complications such as bleeding, and, as such, perhaps more research should be done to improve FOBT as the reference standard for colorectal screening. 
 
Foe further information on CTC, please see the Hayes Directory Report.