New studies find CT scans come with extreme risks

Two studies published in the Archives of Internal Medicine found that CT scans may be much more dangerous than previous studies have shown, contributing to at least 29,000 new cases of cancer every year and causing 14,500 cancer-related deaths.

CT (Computed tomography) scans are a form of medical imaging allow doctors to identify injury, disease, and other problems with three-dimensional images generated on a computer. In addition to their diagnostic use, CT scans ironically are often used for cancer screenings. More recently, some radiologists have used them to administer full-body scans for preventative medicine purposes — a controversial and highly disputed practice.

One of the AIM studies, conducted by Amy Berrington de Gonzalez of the National Cancer institute, analyzed existing data on CT exposure to estimate how frequently patients developed new cancers after a scan. The other study, led by Rebecca Smith-Bindman of the University of California San Francisco, studied 1,119 CT scan patients at four Bay Area hospitals.

Smith-Bindman’s study showed that people receiving CT scans were exposed to four times as much radiation as previously estimated in tests that relied upon dummies with sensors rather than actual humans. The San Francisco hospital tests found that just one CT scan could give patients radiation equivalent to 74 mammograms or 442 chest x-rays.

Younger people are most at risk from the excessive radiation, according to the studies, partly because more future translates to possibly more CT scans, thereby increasing the risk of developing cancer.

For instance, for all the 20-year-old women receiving a single coronary angiogram (a CT scan of the heart), one in 150 will develop cancer because of the procedure.

Smith-Bindman also says that there is no evidence that CT scans are better than other approaches. As many as one-third of all CT scans are unnecessary, according to an editorial in the same volume of AIM.