Computed tomographic (CT) colonography, or virtual colonoscopy, has been shown to be sufficiently accurate in detecting colon cancer. It may be preferred by patients because it is less invasive and better tolerated, and it has become a valid alternative for colorectal cancer screening in the general population.

However, among patients who are at increased risk for colorectal cancer, the accuracy of CT colonography is not well-known. In the June 17, 2009 issue of the Journal of the American Medical Association, researchers report that virtual colonoscopy may be an effective alternative to colonoscopy for screening individuals with a family history of advanced colorectal cancer.

Italian researchers recruited 937 individuals at increased risk of colorectal cancer due to either family history of advanced cancer, personal history of colorectal adenomas, or positive result from fecal occult blood tests (FOBTs, another colorectal cancer screening tool). These asymptomatic individuals each underwent CT colonography followed by colonoscopy on the same day in order to assess the accuracy of virtual colonoscopy in detecting advanced colorectal tumors. Overall, CT colonography identified 151 of 177 participants with advanced tumors of at least 6 millimeters or larger. However, among the participants who were included in the study due to positive FOBTs, virtual colonoscopy seemed to be less accurate.

The researchers comment that, among patients who have positive FOBTs, approximately half end up having an advanced colorectal neoplasm, but up to one-third of FOBT-positive patients fail to follow-up for colonoscopy. Due to this non-adherence, theses study results do not support the use of CT colonography as a first-line strategy for diagnosing colorectal cancer in FOBT-positive patients. However, virtual colonoscopy does seem to have a high accuracy for diagnosing cancer and should, perhaps, be considered for high-risk patients who refuse colonoscopy.

Source:

JAMA. 2009;301(23):2453-2461.