CT Colonography to Screen for Colorectal Cancer and Aortic Aneurysm in the Medicare Population: Cost-Effectiveness Analysis

OBJECTIVE. CT colonography (CTC) is a recommended test for colorectal cancer (CRC) screening according to the updated 2008 American Cancer Society guidelines. CTC can also accurately detect abdominal aortic aneurysm ( AAA). This collaborative gastroenterology-radiology project evaluated the cost-effectiveness and clinical efficacy of CTC in the Medicare population. MATERIALS AND METHODS. A computerized Markov model simulated the development of CRC and AAA in a hypothetical cohort of 100,000 U. S. adults >= 65 years old. Screening with CTC at 5- and 10-year intervals using a 6-mm size threshold for polypectomy was compared with primary optical colonoscopy screening every 10 years and with no screening. Base case costs for CTC and optical colonoscopy were $674 and $795, respectively. The costs of the imaging workup for extracolonic findings at CTC were also included. RESULTS. CTC resulted in 7,786 and 7,027 life-years gained at 5- 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. 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 5- year CTC, 10-year CTC, and 10-year optical colonoscopy strategies, respectively. The ICER of 5- year CTC and 10-year CTC versus optical colonoscopy was $23,234 and $2,144 per life-year gained, respectively. CONCLUSION. Because of its ability to simultaneously screen for both CRC and AAA, CTC is a highly cost-effective and clinically efficacious screening strategy for the Medicare population.