Risks and Benefits of CT Scans in Children

A new study, published earlier this year in The Lancet, presented real patient data on the risks of cancer from CT scans in kids (Lancet. 2012;380:499-505). Though small, the risks were statistically significant and showed a relationship with dose. The study received quite a bit of mainstream news coverage and raised the issue, once again, of how best to weigh the benefits of CT scans against their risks, especially in pediatric patients.

Concerns about the increasing use of medical imaging and the concomitant risks of radiation exposure have been around for some time. In 2008, the World Health Organization launched an initiative to decrease unnecessary exposure. In 2010, the U.S. Food and Drug Administration began its own initiative to promote safe use of CT scans (and other medical imaging tests), including efforts to improve clinical decision-making and increase patient awareness.

One certainty is that overall use of CT scans is on the increase. A 2009 study found a three-fold increase in the number of CT scans run over a 15-year period, culminating in 72 million CT scans in 2007 (Arch Intern Med. 2009;169(22):2071-2077). About 7 percent of those scans were run in children. Not only are children more sensitive to the damaging effects of radiation, but they also have a longer potential life span in which that damage can morph into cancer.

How much otolaryngology has contributed to the increased number of tests is not precisely known. It’s also unclear how the availability of in-office CT scanners—and the potential reimbursability of their use—may influence an individual physician’s practice.

The Risks

Despite all this concern about medical radiation, quantifying potential cancer risks has been largely a theoretical exercise to date. Using data from the biggest doses of radiation ever given—the atomic bombs dropped on Japan in World War II—scientists have tried to estimate dose-related risks based on incidence of cancers developed after the bombings and patients’ distance from the impact site.

“People have always been concerned but have never been able to collect actual data,” said Alan Craft, MD, emeritus professor of child health at Newcastle University in the U.K. and one of the authors of the Lancet study, which he calls the first to have enough CT scans and enough cancers to do the analysis. “The results are not surprising. They’re telling us what we thought.”

The Lancet study examined every person younger than age 21 who received a CT scan through the U.K.’s National Health Service between 1985 and 2002. These patients were cross-checked with U.K. cancer registries for leukemia and brain cancer. Doses absorbed by bone marrow and brain tissue were estimated for each type of CT scan given based on typical machine settings in young people and were adjusted over time, thus accounting for lower doses per test in later years of the study window.