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Due to its capability to simultaneously screen for colorectal cancer (CRC) and abdominal aortic aneurysm (AAA), CT colonography (CTC) is a highly cost-effective and clinically efficacious screening strategy for the Medicare population, according to a study in the May issue of the American Journal of Roentgenology. CTC is a recommended test for CRC screening according to the updated 2008 American Cancer Society (ACS) guidelines. However, Perry J. Pickhardt, MD, from department of radiology at the University of Wisconsin School of Medicine and Public Health in Madison, and colleagues developed a collaborative gastroenterology-radiology project to evaluate the cost-effectiveness and clinical efficacy of CTC in the Medicare population.

The researchers developed a computerized Markov model simulated the development of CRC and AAA in a hypothetical cohort of 100,000 U.S. adults at least 65 years old. They compared screening with CTC at five- and 10-year intervals using a 6-mm size threshold for polypectomy with primary optical colonoscopy screening every 10 years and with no screening.

The authors noted that the base-case costs for CTC and optical colonoscopy were $674 and $795, respectively. They also included costs of the imaging workup for extracolonic findings from CTC.

Pickhardt and colleagues found that CTC resulted in 7,786 and 7,027 life-years gained at five- and 10-year intervals, respectively, compared with 6,032 life-years gained with 10-year optical colonoscopy. The increase in overall efficacy with CTC was primarily due to prevention of AAA rupture because CRC prevention and CRC detection rates were similar for CTC and optical colonoscopy.

The investigators said that all three strategies were highly cost-effective compared with no screening, with an incremental cost-effectiveness ratio (ICER) of $6,088, $1,251, and $1,104 per life-year gained for five-year CTC, 10-year CTC, and 10-year optical colonoscopy strategies, respectively. The ICER of five-year CTC and 10-year CTC versus optical colonoscopy was $23,234 and $2,144 per life-year gained, respectively.

The researchers wrote that the results of the study "clearly show that even with conservative input assumptions, CTC is an extremely cost-effective CRC screening option for the Medicare population particularly when the added benefit of AAA screening is considered. Furthermore, CTC imparts a positive benefit from CRC screening that is similar in magnitude to optical colonoscopy but that entails significantly fewer invasive procedures."

"Given the dire need for increased CRC screening among Medicare beneficiaries, we believe that CTC should be implemented as soon as possible because it has met or has exceeded the key benchmarks achieved by optical colonoscopy and the other currently approved screening options," the authors concluded.