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Wall Street Journal

Two Studies Recommend Less-Frequent Colon Exams


September 23, 2008            

                Two new large medical studies recommend less frequent and less invasive colon exams for most people over 50.

Colon exams are recommended for everyone over 50 to prevent colon cancer, the second biggest cancer killer in the U.S., with some 52,000 deaths last year. Doctors use the exams to find, and if necessary remove, harmless growths before they become cancerous, but the screening process can be expensive and unpleasant.

The studies both appeared in this week's New England Journal of Medicine. One found that a less invasive procedure, called computed tomographic, or CT, scans are as effective in detecting pre-cancerous growths as optical colonoscopies, in which a probe is inserted into the rectum. The computerized scans cost about half as much as a colonoscopy and don't involve sedation.

Both processes do require bowel preparation by taking strong laxatives, which many patients find the worst part of the screening.

The second study, which involved 1,256 patients who had tested negative for growths, found that five years later, none of the patients had developed colon cancer. The study leader, Dr. Thomas Imperiale of Indiana University School of Medicine in Indianapolis, concluded that for patients with low-risk factors, a ten-year interval between screenings is sufficient.

It isn't clear how much the studies will affect clinical practice. Some medical groups already recommend either CT scans or colonoscopy as the best way to detect pre-cancerous growths, but many doctors push patients toward colonoscopies. Both tests are considered much more accurate than less expensive techniques like blood tests. Many doctors and Medicare currently recommend rescreening for healthy patients every 10 years.

Robert H. Fletcher, professor emeritus at Harvard Medical School, Boston, wrote in an editorial that "now we can be more confident" that it's safe to choose "10-year intervals ... and CT colonography," instead of a colonoscopy.

The study of CT scans collected data on 2,531 patients at 15 study centers around the country. All of them were tested with both a CT scan and a colonoscopy. The scan picked up all but 10% of the large growths that were found with the colonoscopy. That's equivalent to the accuracy of colonoscopies, as determined by previous studies. Daniel Johnson, chairman of the radiology department at Mayo Clinic, Scottsdale, Ariz., who led the study said, "None of the exams are perfect. This would put [the two methods] very close."

He noted that most patients prefer CT scans because "you don't get sedated and you can go back to work" that day. In addition, he said, a CT scan costs about $600 to $1,200, which is about half the amount widely charged for a colonoscopy. He predicts that if more doctors begin to recommend CT scans, more people will get screened.

Write to William M. Bulkeley at