A large study reveals that high-dose radiation from CT scans puts younger patients, especially girls, at a higher risk of developing cancer.

If your child’s pediatrician orders a computed tomography (CT) scan, it’s important to ask what other diagnostic options are available. Medical researchers are now reporting that for children, the risk of cancer from radiation exposure is too high a price to pay for diagnostic certainty.

According to a study published today in JAMA Pediatrics, CT use in children from birth to age 15 has increased markedly over the past two decades. And the ionized radiation doses delivered by CT scans are higher than the doses delivered though conventional radiology, at levels that have been linked to significantly higher risks of cancer.

Using data from seven U.S. healthcare systems, Diana L. Miglioretti, Ph.D., of the University of California, Davis, and her colleagues quantified CT-use trends in pediatrics and estimated the future risk of radiation-induced cancer in these children.

“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,” the study authors noted.

Computed tomography has been widely used in the U.S. since the late 1970s. According to the study, between 1996 and 2005, the use of CT scans doubled for children younger than 5 and tripled for children ages 5 to 14. Since 2005, the number of pediatric CT scans remained stable then declined through 2010.

The study included 152,500 to 371,000 children in a given year for a total of nearly five million children. With an estimated 4.25 million CT scans performed on children in the U.S. each year, 4,870 childhood cancers are expected to occur annually.

The ionized radiation doses delivered during CT scans are 100 to 500 times higher than the doses delivered though conventional radiology. Effective doses range widely—from 0.03 to 69.2 mSv per scan. Based on their calculations, Miglioretti and her colleagues suggest that reducing the highest 25 percent of doses to the median (midpoint) may prevent 43 percent of these childhood cancers every year.

“Children are more sensitive to radiation-induced carcinogenesis [cancer growth] and have many years of life left for cancer to develop,” the authors note in the study background.

The dangers of radiation are greatest for girls, especially from CT scans of the abdomen or pelvis, chest, and spine. For example, one in every 300 to 390 abdomen or pelvis scans is projected to cause radiation-induced solid cancer, as are one in 330 to 480 chest scans, and one in 270 to 800 spinal scans, depending on the girl’s age.

The highest risk of radiation-induced solid cancer was associated with abdominal or pelvis scans. The use of these scans has increased the most dramatically in recent years, especially for older children. Most of these scans were for complaints of pain, possible appendicitis, or infection. The authors suggest ultrasound testing as a reasonable alternative for identifying appendicitis.

The risk of leukemia and brain cancer was highest from head CT scans for children younger than 5, according to the study authors. Leukemia is the most common cancer in children and teens, accounting for 31 percent of all childhood cancers.

Image Gently, a nonprofit organization that promotes radiation safety in pediatric imaging, offers resources for parents and certification programs for physicians and radiologists. The organization has developed standardized pediatric CT protocols to ensure that, when the case is strong for the use of a CT scan, the radiation dose is as low as possible.

“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,” the study authors wrote.

In an accompanying editorial, Alan R. Schroeder, M.D., of the Santa Clara Valley Medical Center in San Jose, and Rita F. Redberg, M.D., editor of JAMA Internal Medicine, said that the benefits of CT scans in children do not outweigh the risks. They urged physicians to use caution in ordering CT scans for kids, saying that minimizing radiation exposure should be a high priority.

“This will require a shift in our culture to become more tolerant of clinical diagnoses without confirmatory imaging, more accepting of ‘watch and wait’ approaches, and less accepting of the ‘another test can’t hurt’ mentality,” wrote Schroeder and Redberg.

“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,” Miglioretti and her colleagues concluded.