CT colonography is a more clinically effective and more cost-effective screening strategy over colonoscopy with or without ultrasonography, according to a computerized model simulation published in the April 14 issue of the Archives of Internal Medicine.

Cesare Hassan, MD, from the gastroenterology and digestive endoscopy unit at Nuovo Regina Margherita Hospital in Rome, and colleagues said that for detecting colorectal neoplasia, abdominal CT with colonography technique (CTC) can detect unsuspected extracolonic cancers and abdominal aortic aneurysms (AAA). However, the researchers said they undertook the study to investigate the efficacy and cost-effectiveness of the combined abdominal CT screening strategy.

The researchers constructed a computerized Markov model to simulate the occurrence of colorectal neoplasia, extracolonic malignant neoplasm and AAA in a hypothetical cohort of 100,000 subjects from the United States who were 50 years old. The investigators simulated screening with CTC, using a 6 mm polyp-size threshold for reporting, and compared it with a competing model of optical colonoscopy (OC), both without and with abdominal ultrasonography for AAA detection (OC-US strategy).

In the simulated population, Hassan and colleagues found that CTC was the dominant screening strategy, adding 1,458 life-years versus optimal colonoscopy and 462 life-years versus optimal colonoscopy along with one-time abdominal ultrasound.

The authors wrote that CTC was also less costly, with a savings of $266 per person compared to optimal colonoscopy, and a savings of $449 per person versus optimal colonoscopy and one-time abdominal ultrasound.

The researchers noted that the additional gains for CTC were largely due to a decrease in AAA-related deaths, whereas the modeled benefit from extracolonic cancer downstaging was a relatively minor factor.

With a sensitivity analysis, OC-US became more cost-effective only when the CTC sensitivity for large polyps dropped to 61 percent or when broad variations of costs were simulated, such as an increase in CTC cost from $814 to $1300 or a decrease in OC cost from $1100 to $500, the authors wrote.

The researchers also reported that the estimated mortality from CT-induced cancer was less than estimated colonoscopy-related mortality (8 vs. 22 deaths), both of which were minor compared with the positive benefit from screening.

In fact, all three screening strategies were found to be cost-effective compared with no screening.

“CTC was dominant because it was the most cost-effective and clinically effective option,” the authors concluded.