However, it’s important to note that the virtual colonoscopies were done without laxative preparation.
In addition, optical colonoscopies found more advanced lesions (large polyps and cancers) than CT colonography.
However, as an overall strategy, the yield of advanced lesions per 100 people invited to participate in screening was the same because more people agreed to have a CT colonography.
Dutch researchers randomly invited nearly 9,000 people, aged 50 to 74, living in areas around Amsterdam and Rotterdam to participate in colorectal cancer screening either by traditional colonoscopy or CT colonography. Twice as many were invited for colonoscopy as CT colonography.
CT colonography was done without the usual harsh laxative preparation, but patients were given medicine to “tag” feces.
If CT colonography exams found cancer or polyps bigger than 9 millimeters, doctors referred patients on for a colonoscopy. For smaller polyps 6 to 9 millimeters, surveillance with further CT colonography was recommended.
The research team found:
- For colonoscopy, 5,924 people were asked and 1,276 agreed — 22 percent.
- For CT colonography, 2,920 were asked and 982 agreed — 34%.
- 9 percent (111) of those having colonoscopy had an advanced adenoma or cancer.
- 6 percent (60) of those having CT colonography had an advanced lesion.
- 8.7 advanced lesions were found for every 100 invited people with colonoscopy compared to 6.1 advanced adenomas or cancer for those who had CT colonography — a similar “yield” per invitee.
Esther M. Stoop, MD and her colleagues concluded,
Participation in colorectal cancer screening with CT colonography was significantly better than with colonoscopy, but colonoscopy identified significantly more advanced neoplasia per 100 participants than did CT colonography. The diagnostic yield for advanced neoplasia per 100 invitees was similar for both strategies, indicating that both techniques can be used for population-based screening for colorectal cancer. Other factors such as cost-effectiveness and perceived burden should be taken into account when deciding which technique is preferable.
In an editorial accompanying the article in The Lancet Oncology, radiologist Dr. Perry Pickardt said,
The bottom line is quite simple—too many people are dying of a readily preventable disease. The issue with screening for colorectal cancer is not related to test efficacy per se, but rather to the willingness of patient participation (and study availability). By offering the additional option of CT colonography for screening, overall patient outcomes will be positively affected by the equivalent (or greater) yield for advanced neoplasia coupled with a decrease in complications and costs.
Of note, both colonoscopy and CT colonography confer the crucial advantage of cancer prevention through detection (and removal) of advanced adenomas over the cancer detection aspect alone that is provided by current stool-based testing. The additive yields of having both colonoscopy and CT colonography available as primary screening options could have a profound effect on the incidence and mortality of colorectal cancer in the future.
Dr. Pickardt also pointed out that the CT colonography in the study was done without laxative preparation and using an older two-dimensional CT reading. Other studies with bowel prep and three-dimensional readings have found both methods equivalent in finding advanced polyps and cancer.