Available scanners tackle future CTC screening demand

Showing CT colonography's value for cancer screening was one thing. Proving it could handle the volume of patients who may need the test in years to come, however, is an entirely different task. Researchers say not to fret.

CT colonography's validation in clinical trials as an effective cancer screening method on a par with colonoscopy made big headlines recently. The news became even sweeter to CTC advocates after the American Cancer Society and the American Gastroenterological Association endorsed the minimally invasive procedure.

The next step in this chain of events was establishing whether the installed base of multislice CT scanners was large enough to handle screening. Although the impact of introducing CT colorectal cancer screening at the national level upon available MSCT units remains unknown, calculations suggest they may be sufficient to handle the task, said Dr. David H. Kim, coauthor of a study that looked into the issue.

Kim, an assistant professor of abdominal imaging at the University of Wisconsin-Madison, and colleagues used mathematical probability models to determine the average number of CTC scans per day that would be needed to do screening based on the number of scanners available nationwide. They included only MSCT scanners, following the premise that single-detector units were inadequate to perform CTC, he said. Their baseline analysis found that an estimated 37.2 million eligible adults would need to undergo CTC screening over a 10-year period.

Minding the appropriate variables for subject age and screening intervals, they estimated CTC screenings should go at a rate of about one to 1.5 studies per unit daily. None of all the several possible variables that could come into play would have a significant impact on final outcomes, Kim said. Even by assuming compliance rates near 90%, each MSCT scanner available in the country would not have to produce more than two studies per day. Current compliance rates for breast cancer screening approach 75%.

Kim presented his group's results at the 2008 American Roentgen Ray Society meeting in Washington, DC.

The calculation models make conservative assumptions and probably underestimate true MSCT scanner capacity in the U.S., Kim said. He warned, however, that the study did not address staffing, training, or geographic variables.Radiologists have followed with excitement these announcements, particularly the endorsements of CTC by other subspecialty groups that boost hopes of an expedient approval of reimbursement for CTC.

"The endorsement by the gastroenterologists may have been as crucial as the endorsement by the Cancer Society," said Dr. James H. Thrall, chair of radiology at Massachusetts General Hospital. "The issue is moving CTC from experimental to reimbursed. Without the AGA, it would have set the clock back at least one or two years. Now we have a legitimate expectation for 2009."