Magnified colon polyp via CT colonography is shown in 3D. Image Source: David J. Vining, MD, University of Texas MD Anderson Cancer Center in Houston

CT colonography (CTC), or virtual colonoscopy, is not cost-effective if reimbursed at the same rate as colonoscopy, based on a study published online July 27 in the Journal of the National Cancer Institute. However, the accompanying editorial noted that cost-effectiveness analyses are useful, but that they often cannot include some important considerations.

Colon cancer is one of the most common cancers in people over the age of 65, and there are several screening methods used to detect it.

To investigate whether CTC screening every five years could be cost effective compared to currently reimbursed colorectal screening tests, Amy B. Knudsen, PhD, of the Institute for Technology Assessment at Massachusetts General Hospital in Boston, and colleagues used simulation models to study an unscreened cohort of Medicare beneficiaries.

They computed the incremental cost-effectiveness ratios for the currently reimbursed screening tests and calculated the maximum cost per scan (i.e., the threshold cost) for the CTC strategy to lie on the efficient frontier. Sensitivity analyses were performed on key parameters and assumptions.

The researchers used three simulation models to calculate the lifetime costs and life expectancy associated with 15 screening strategies, including no screening, CTC screening every five years, annual fecal occult blood test (FOBT), flexible sigmoidoscopy every five years, flexible sigmoidoscopy every five years in conjunction with the annual FOBT and colonoscopy every 10 years. They evaluated these strategies for a previously unscreened population of Medicare beneficiaries, starting at age 65.

The number of life-years gained from five-yearly CTC was only slightly lower than the number gained from 10-yearly colonoscopy screening, the authors reported. However, they found that if CTC was reimbursed at $488, which is approximately the same rate as colonoscopy, then lifetime costs associated with CTC screening exceed those of colonoscopy.

Nevertheless, Knudsen and colleagues also found that "if the availability of CTC enticed 25 percent of otherwise unscreened individuals to be screened, CTC would be cost-effective" at this reimbursement rate. The Centers for Medicare & Medicaid Services does not currently reimburse CTC screening, and it is unclear if more individuals would adopt colon cancer screening if offered CTC, according to the authors.

The researchers found that the range at which reimbursement would be cost-effective would be $108 to $205 per scan.

"If CTC screening is reimbursed at roughly the same rate as colonoscopy, the cost, relative to the benefit derived and to the availability and costs of other colorectal screening tests, is too high for it to be a cost-effective screening strategy," the authors concluded. “CTC could be a cost-effective option for colorectal cancer screening among Medicare enrollees if the reimbursement rate per scan is substantially less than that for colonoscopy or if a large proportion of otherwise unscreened persons were to undergo screening by CTC.”

The study also "highlights that comparative effectiveness research, and cost-effectiveness analyses in particular, can also be used to inform reimbursement levels.”

In an accompanying editorial, Russell Harris, MD, of the Cecil G. Sheps Center for Health Services Research at the University of North Carolina in Durham, N.C., raises doubts about the safety and efficacy of both CTC and colonoscopy.

Harris noted how the cost-effectiveness analysis could not include some of the potential harms of both CTC and colonoscopy.

CTC often finds abnormalities outside the colon—in such areas as the kidneys or adrenal glands—that lead to further tests and procedures but likely not to longer life, he wrote. Colonoscopy often leads to removal of small polyps unnecessarily, sometimes leading to complications such as bleeding, said Harris.

Suggesting that neither CTC nor colonoscopy are ideal screening tests, Harris concluded: "Wouldn't it be interesting if we ended up, a few years from now, with neither CTC nor colonoscopy as the primary screening test, but rather an improved fecal test as our gold standard."