Radiology: Virtual colonoscopy effective screening tool in older patients

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CT colonography, also known as virtual colonoscopy, can be used as a primary screening tool for colorectal cancer in adults over the age of 65, according to a study published online Feb. 23 in Radiology.

Previous studies have found no significant difference between the diagnostic accuracy of virtual colonoscopy and traditional optical colonoscopy. C. Daniel Johnson, MD, professor and chair of radiology at Mayo Clinic in Scottsdale, Ariz., and colleagues wanted to see if both exams are as equally effective for adults over 65 as they are for adults between 50 and 65 years old.

The researchers conducted a follow-up analysis of data from the National CT Colonography Trial, in which 2,600 patients over the age of 50 underwent both virtual and optical colonoscopies at 15 centers in the U.S.

Of the patients in the trial, Johnson et al focused on data from 477 patients over the age of 65 and 2,054 patients between the ages of 50 and 65 who were screened for polyps using the two procedures.

Results showed cancerous lesions 1 centimeter or larger were found in 6.9 percent of patients in the 65 years and older group and in 3.7 percent of the younger patients.

There was no significant difference in the accuracy of CT colonography for the detection of large- and intermediate-sized cancers in the older participants compared to the younger participants. Sensitivity and specificity among the older group was 0.82 and 0.83, respectively. In the younger group, sensitivity was 0.92 and specificity was 0.86.

“We found no statistical difference in the diagnostic performance between the two patient groups,” Johnson said in a statement. “This is good information for patients of any age, as they can consider CT colonography as a valid option for colorectal cancer screening.”

Colorectal cancer is the third most commonly diagnosed cancer in both men and women and the third leading cause of cancer deaths in the U.S. According to the American Cancer Society (ACS), a decline in colorectal cancer incidence rates over the last two decades is largely attributable to screening tests that allow polyps to be removed before they progress to cancer.

Despite the effectiveness of colorectal cancer screening, the ACS estimates that only half of the U.S. population older than age 50 is being screened as recommended for the disease. Experts point to cost and a lack of access to healthcare as contributing factors.

Although both optical and virtual colonoscopy procedures typically require the use of laxatives to empty the colon prior to the test, there are major differences between the two exams. Most notably, traditional colonoscopy requires sedation due to the risk of bowel perforation.

“For the older patient, the risks of and recovery from sedation are issues,” said Johnson.

CT colonography, although quicker and half as costly as optical colonoscopy, involves exposure to low doses of radiation and must be repeated more often. When polyps 6 millimeters or larger are detected by CT colonography, the patient must undergo an optical colonoscopy to have them removed. In addition, incidental CT findings outside the colon might require additional follow-up.

Johnson said there isn’t a fight between CT colonography and colonoscopy, rather he want patients to be screened with the appropriate test. “CT colonography is a preferred test for some patients and should be an option. Patients should talk to their doctors and choose the best option for them.”