Understanding a virtual colonoscopy

According to a new study CT colonography, a less invasive option to colonoscopy, could offer patients who are at a raised risk of colorectal cancer an alternative to colonoscopy. The results indicated that compared with colonoscopy, CT colonography had a negative predictive value of 96.3% overall in high-risk patients.

The far less evasive screening method, which uses X-rays and computers to produce 3-D images of the colon, identified 85% of suspicious growths in people who had elevated risks for colorectal cancer in the newly published study conducted in Italy.

The results of the study, published in the Journal of the American Medical Association, adds to a growing body of evidence showing the CT procedures are safe and almost as good as standard colonoscopies.

Daniele Regge, M.D., of the Institute for Cancer Research and Treatment in Turin, Italy, studied 937 patients, including 373 with a family history of colorectal cancer, 343 with a personal history of adenomas, and 221 with a positive fecal occult blood test. All patients underwent CT colonography as well as colonoscopy.

A CT scan is “better accepted than colonoscopy,” said Regge. “Thus, it may help increase the low adherence reported for individuals who are candidates for screening.”

CT colonography correctly identified 85% of patients with early cancerous lesions as well as 88% of patients with no lesions. The odds that a patient who received a positive result with CT colonography did indeed have such a lesion was 62%. The likelihood that someone who received a negative result truly did not have such a lesion was 96%.