TUESDAY, Aug. 31, 2004 (HealthDayNews) -- Body scans, a screening tool that many have touted as a way to catch cancer early, may actually increase the risk of disease if used too often.

The chances of dying from cancer caused by radiation from a full-body CT scan is low when done only once, but a new study finds the danger increases dramatically if the scan is performed every year or two.

These scans are an elective procedure that has become increasingly popular, and as more seemingly healthy people get them, researchers have become concerned about the potential risk.

"CT scans, by their nature, produce high radiation doses," explained lead researcher David J. Brenner, a professor of radiation oncology and public health at Columbia University Medical Center.

In terms of benefits, Brenner said there have not been any studies yet that have showed longevity or health is improved by having a scan or a series of scans.

Brenner and his colleague, Carl D. Elliston, wanted to find out the risk for a fatal cancer caused by a full-body CT scan. The researchers knew the radiation dose from a full-body CT scan is similar to the doses of radiation received by some survivors of the atomic bombs at Hiroshima and Nagasaki, Japan, during World War II. They also knew those survivors faced an increased cancer risk.

Using that data, the researchers calculated the risk of developing a fatal cancer from the radiation used in a full-body CT scan. Brenner added that older people tolerate radiation better.

The study appears in the September issue of Radiology.

For someone aged 45, the risk of developing a fatal cancer from a single full-body CT scan is about one in 1,200, "meaning that if 1,200 people had one scan, you might expect one of them to die of a radiation-induced cancer, which is not a huge risk," Brenner said.

However, if you have a scan every year or every couple of years, the radiation dose accumulates, and so does the risk, he said. "A 45-year-old who has one of these scans every year for 30 years, the risk is one in 50," he added.

"There you have a very substantial risk, so the benefit would have to be more than that to justify using this procedure," Brenner said. "And right now, we don't have evidence of the benefits."

"It's probably premature to consider having these tests until we really understand the benefits better, knowing what the risks are. It's a questionable decision to make at this point," Brenner said.

Another expert also urged caution.

"Whole-body CT scans are not recommended because we do not have evidence that they confer net benefit. This paper by Brenner is important for highlighting the potential harm," said Dr. David L. Katz, an associate clinical professor of public health and director of the Prevention Research Center at Yale University School of Medicine.

"Why would you voluntarily have a test not known to confer benefit, pay for it, and incur a cancer risk some 10,000 times greater than that associated with dioxin?" he added.

Katz noted that high-end medical businesses are making money by peddling such technology with very convincing advertisements.

"Confer with a trusted health-care provider about what tests to have and what tests to avoid," Katz said. "When it comes to whole-body CT scans, step away from the radiation, and your checkbook, and you'll be much better off," he advised.

More information

The U.S. Food and Drug Administration can tell you about full-body CT scans.

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