CT colonography: screening in individuals at high risk for colorectal cancer.

The use of computed tomographic colonography (CTC) as a screening test for colorectal cancer is being advocated with growing enthusiasm by physicians and the public as stronger evidence of its validity and limited invasiveness emerges from the literature. Because the approach to surveillance of colorectal cancer depends on an individual's degree of risk category, which depends on familial and personal histories, it seems logical that the diagnostic performance and cost efficacy of screening CTC may differ according to the characteristics of the target population. Although CTC seems a valid option in low- to average-risk populations, pending a careful assessment of its cost and estimates of its cost efficacy, there are some important issues that should be addressed when it comes to considering its use in high-risk patients. The expected larger number of induced colonoscopies and higher false-positive rates are likely to have a great influence on CTC costs, but if its implementation causes a dramatic increase in the number of patients willing to undergo screening, thanks to its acceptability, then the cost efficacy ratio may ultimately become competitive with all other screening strategies for colorectal cancer. We strongly feel that large and well-conducted trials are needed to clarify the role of CTC in screening patients at increased risk of developing colorectal cancer.