The 4 million pediatric CT scans of the head, spine or abdomen/pelvis performed each year are projected to cause nearly 5,000 future cancers, according to a study published in the August issue of JAMA Pediatrics.

This relatively small, but significant, risk can be reduced by dose reduction and appropriate imaging initiatives, which have the potential to prevent more than half of the projected radiation-related cancers, according to Diana L. Miglioretti, PhD, of the University of Washington, Seattle, and colleagues.

“The increased use of CT in pediatrics, combined with the wide variability in radiation doses, has resulted in many children receiving a high-dose examination,” wrote the authors. “Dose-reduction strategies targeted to the highest quartile of doses could dramatically reduce the number of radiation-induced cancers.”

Miglioretti and colleagues conducted a retrospective observational study of children younger than 15 years of age who underwent CT scanning at one of seven U.S. healthcare systems. All cases were from 1996 to 2010, which included 4,857,736 child-years of observation. Radiation doses were calculated for a random subset of 744 scans conducted between 2001 and 2011.

Utilization rates followed the same pattern of rise, plateau and fall that broader analyses of advanced imaging have demonstrated in recent years. CT use doubled for children younger than five years of age between 1996 and 2005, and tripled for children five to 14. Rates were steady in 2006 and 2007, before beginning to decline in recent years.

Effective doses varied widely, from 0.03 to 69.2 mSv per scan, reported the authors. Between 14 percent and 25 percent of abdomen/pelvis scans delivered an effective dose of 20 mSv or higher. Up to 14 percent of spine scans and 8 percent of chest scans had effective doses in this range.

Factoring in the higher risks for younger patients and girls, Miglioretti and colleagues calculated that 4,870 future cancers would result from the 4 million CT scans performed each year in children younger than 15 years old.

Targeted high-dose scans, however, could make a huge dent in the number of future cancers, according to the authors. If the highest 25 percent of doses were reduced to the median, as many as 43 percent of CT-induced cancers can be prevented. “We estimate that reducing the highest 50 percent of doses to the median would only prevent another 8 percent of cancers; thus, the biggest potential gains come from focusing on the highest 25 percent of doses.”

By also eliminating unnecessary scans—which could be as many as one third of pediatric CTs, according to some estimates—the dual strategy of encouraging dose reduction and appropriate imaging could potentially prevent 62 percent of radiation-related cancers.

“Thus, more research is urgently needed to determine when CT in pediatrics can lead to improved health outcomes and whether other imaging methods (or no imaging) could be as effective,” wrote Miglioretti and colleagues. “For now, it is important for both the referring physician and the radiologist to consider whether the risks of CT exceed the diagnostic value it provides over other tests, based on current evidence.”