Italian Study Shows CT Colonoscopy Offers npv of 96.3%

COLORECTAL CANCER (CRC) is the most common cause of cancer-related death in non-smoking Americans and the second most common cause of cancer-related deaths in smokers (behind lung cancer). The American Cancer Society estimates that this year there will be about 99,200 new cases and 48,100 deaths from colon cancer and 37,200 new cases and 8,600 deaths from rectal cancer.

Computed tomographic (CT) Colonography has been shown to be sufficiently accurate in detecting colorectal neoplasia. Less invasive and better tolerated than colonoscopy, CT Colonography is now considered a valid alternative for CRC screening in the general population and is now recommended by the American Cancer Society as a preferred front-line screening test in average risk individuals. However, less information is available on its performance in individuals at increased risk of CRC. In the June 17, 2009 edition of the Journal of the American Medical Association is a study designed to assess the accuracy of CT colonography in detecting advanced colorectal neoplasia in asymptomatic individuals at increased risk of CRC using unblended colonoscopy as the reference standard.

Individuals with first-degree family history of advanced colorectal neoplasia, those who have had resection of colorectal adenomas, and those with positive results from fecal occult blood tests (FOBTs) are at increased risk of CRC. However, adherence to follow-up colonoscopy in these individuals is suboptimal. The aim of this study was to assess sensitivity and specificity of CT Colonography in detecting advanced neoplasia (ie, advanced adenoma or CRC) 6 mm or larger in individuals at increased risk of developing CRC, because of either family history of advanced colorectal neoplasia in first-degree relatives, personal history of adenomas, or positive results from immunochemical FOBTs.

This was a multicenter, cross-sectional study. Individuals at increased risk of CRC due to either family history of advanced neoplasia in first-degree relatives, personal history of colorectal adenomas, or positive results from fecal occult blood tests (FOBTs) were recruited in 11 Italian centers and 1 Belgian center. Each participant underwent CT colonography followed by same-day colonoscopy.

Of 1103 participants, 937 were included in the final analysis: 373 cases in the family-history group, 343 in the group with personal history of adenomas, and 221 in the FOBT-positive group. Overall, CT colonography identified 151 of 177 participants with advanced neoplasia 6 mm or larger and correctly classified results as negative for 667 of 760 participants without such lesions.

The positive and negative predictive values were 61.9% and 96.3%, respectively; after group stratification, a significantly lower negative predictive value was found for the FOBT-positive group.

Conclusions: In a group of persons at increased risk for CRC, CT colonography compared

with colonoscopy resulted in a negative predictive value of 96.3% overall. When limited to FOBT-positive persons, the negative predictive value was 84.9%.

Based on this most recent study, if VC has a NPV of 95% or greater for people who are at high risk (people who were not screened but for diagnosis) then for a screening population the NPV is closer to 99%. If your patient is a reluctant candidate for screening for colon cancer, CTC may be the answer.

Gil Gradisar, President, PrevaHealth