Kids, CT Scans and Cancer Risks

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Cancer risks elevated in young people who have had CT scans

May 21, 2013 / Author:  / Reviewed by: Joseph V. Madia, MD

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(dailyRx News) Computed tomography (CT) scans expose patients to radiation. There’s a suggested link between the imaging tests and increased cancer risks, but nothing has been clearly defined. What are those risks for children?

Children and adolescents who had at least one CT scan had a 24 percent higher risk of developing cancer than did kids who never had the scans, according to a recent study.

While this sounds alarming, the actual number of additional cancer cases among those who underwent CT scans was quite low: less than 10 excess cases per 100,000 people.

"Ask if there is an alternative imaging test to a CT scan."

Epidemiologist John D. Mathews, MD, PhD, of the School of Population and Global Health at the University of Melbourne in Carlton, Australia, led the study.

Dr. Mathews and colleagues looked at Australian Medicare and national cancer records of nearly 11 million youngsters between the ages of 0 and 19 years old.

Of this group, 680,000 had a CT scan at least one year before a cancer diagnosis, and 122,500 of the young people had received more than one scan.

Study members who had undergone scanning were followed for an average of 9.5 years and those who were not scanned were tracked for just over 17 years.

Here’s what the researchers learned:

  • 3,150 (.004 percent) of youngsters exposed to CT scans had developed cancer by the end of 2007.
  • Cancers included malignancies of the brain, digestive organs, soft tissue, female genital, urinary tract and thyroid along with melanoma and blood cancers.
  • Cancer risks were 24 percent higher in patients who had received one CT scan, and risks increased 16 percent for every additional CT scan.
  • Rates of excess cancers among those who were scanned were 9.38 in every 100,000 people.
  • 60 percent of the scans were of the brain, which may have been the reason for – not the result of – CT scans.
  • Brain cancer risks were still elevated 15 years after the first CT scan.
  • The highest risks for brain cancer were seen in children who had their first CT scan before the age of 5.
  • Solid tumor cancer cases increased over time since the first exposure.
  • Overall, increased risks for all cancers declined over time, but were still significantly higher than risks of people who had not been scanned.
  • Girls tended to have greater increased risks than did boys – 23 percent in females versus 14 percent in males.

So what does all this mean? dailyRx spoke to an expert in the field, Aaron Sodickson, MD, PhD, chief of emergency radiology and director of Computed Tomography at Brigham and Women’s Hospital in Boston.

“To me, the most important scientific contribution of this study is that they have confirmed that radiation doses as small as those from CT scans are associated with a small but detectable increase in cancer risk in children and adolescents. We've previously had limited direct data to establish the size of the risk from the small radiation doses used in medical imaging," Dr. Sodickson said.

“It's important to emphasize that these are very small increases in risk, so patients should not be overly concerned by these findings. Nevertheless, as a medical community we have a responsibility to avoid unnecessary radiation exposure to our patients. There are many opportunities to ensure appropriate imaging utilization, and we have many available tools to perform high quality imaging at much lower doses than were possible in the past," said Dr. Sodickson, who wrote an editorial accompanying the article on this study.

The study was published May 21 in BMJ.

This research was funded by the Australian government and supported by in-kind contributions of people funded by the Cancer Research Campaign UK or employed by other agencies. No competing interests were reported.