Alternative Screening for Colon Cancer

A colonoscopy is the normal method of screening for colon cancer, but it is invasive and unpleasant.

Now there is news of an alternative method called computed tomographic colonography (CTC) which has been developed over the past few years. This method is also known as “virtual colonoscopy” because it’s minimally invasive, requiring a catheter to be inserted into the rectum to fill the colon with air, followed by non-invasive optical scan. It may be less invasive, but is it as effective in detecting colon cancer? A study in the New England Journal of Medicine reported this month on US researchers at the University of Wisconsin Medical School who set out to find the answer. They compared similar numbers of patients who had undertaken one or other of the screening methods and found that with traditional colonoscopy screening 123 advanced tumours were found, compared to 121 in the CTC group which is not a significant difference statistically, but vital to the two people whose tumours were detected.

There is a drawback to traditional screening in that perforating the colon during the procedure is a risk, and in fact this occurred on 7 occasions during the study while it is obviously not a risk with CTC.

Another difference is that traditional colonoscopy routinely removes all polyps that are detected, and in fact 2,434 were removed as against only 561 for those having CTC screening. This huge difference is not about whether the polyps are detected, but arose from the fact that patients were given the option of leaving very small polyps in place or undergoing an additional procedure to remove them. It’s certainly true that very small polyps may never become a problem, but with a traditional colonoscopy they are automatically removed before they can develop further. However, in the Wisconsin study 8% of the patients underwent a follow-up colonscopy after undergoing CTC.

On balance the researchers concluded that traditional colonoscopy was still the safest and most effective screening treatment at the moment.