CT heart scans: risk climbs as age at screening falls.

Use of computed tomography (CT) scans to investigate heart blockages is becoming common, especially for people entering emergency rooms with severe chest pain. A new study quantifies a downside to these rapid and relatively noninvasive scans: Their X rays can substantially increase an individual's cancer risk. Younger patients, especially women, incur the greatest increases.

Andrew J. Einstein of Columbia University Medical Center and his colleagues employed computer modeling to calculate radiation exposures to organs as would occur during CT scanning of a man's or woman's heart. The researchers then estimated the likelihood that these phantom organs would develop cancer. They did this by comparing the estimated X-ray doses to those corresponding to age- and gender-adjusted cancer risks in the National Academy of Sciences' most recent report on radiation effects.

Among the men, the team concludes, each scan at age 20 increases the lifetime chance of developing cancer by 1 in 686. The extra lifetime-cancer risk from a scan of an 80-year-old man would be 1 in 3,261. By contrast, a 20-year-old woman's extra cancer risk from a scan is probably 1 in 143, and an 80-old-woman would gain a 1 in 1,338 risk of cancer from a CT heart scan. The researchers report their calculations in the July 18 Journal of the American Medical Association.

Younger patients may experience greater risks because precancerous changes in their tissues have more time to mature, Einstein says. Moreover, he notes, breast tissue--heavily exposed in these scans--is more radiation sensitive in women than in men.

The findings, Einstein concludes, suggest that CT scans should be largely restricted to older patients at high risk of heart disease.--J.R.