Efforts to reduce the highest radiation doses administered to children who undergo CT scans, as well as the elimination of unnecessary scans, may reduce incidence of radiation-induced cancers by nearly two-thirds, according to results of a retrospective, observational study.
“Children tend to absorb more radiation from imaging than adults do because their bodies are smaller,” Diana L. Miglioretti, PhD, a senior investigator at Group Health Research Institute in Seattle, said in a press release. “The radiation children absorb will lead to greater harm because they are more likely than adults to develop cancer from radiation exposure. That’s why radiology technologists should use lower settings for children than adults. But that doesn’t necessarily always happen.”
Diana L. Miglioretti
Eligible study participants included children aged 15 years or younger who had a CT scan between 1996 and 2010 at one of seven health care systems in the United States.
Miglioretti and colleagues calculated radiation doses for 744 CT scans performed between 2001 and 2011, and the analysis included 4,857,736 child-years of observation.
Rates of CT use, organ and effective doses, and projected lifetime attributable cancer risk served as the primary outcome measures.
Between 1996 and 2005, CT use doubled in children aged younger than 5 years and tripled among children aged 5 to 14 years. The rate remained stable during 2006 and 2007, then declined thereafter.
The range of effective doses varied from 0.03 mSv to 69.2 mSv per scan. An effective dose of at least 20 mSv was administered to varying degrees at several sites, including the abdomen/pelvis (14%-25%), spine (6%-14%) and chest (3%-8%).
Younger patients and girls were at increased likelihood for a higher projected lifetime attributable risk for solid cancer, according to researchers. Children who underwent abdomen/pelvis or spine scans also were at increased risk for these cancers.
Among girls, depending on the age, a solid cancer induced by radiation is projected to result from 300 to 390 scans in the abdomen/pelvis, 330 to 480 chest scans and 270 to 800 scans in the spine.
Among children aged younger than 5 years, the risk of leukemia was highest from head scans (1.9 cases per 10,000 scans).
The roughly 4 million pediatric CT scans of the head, abdomen/pelvis, chest or spine performed nationally each year are projected to cause an estimated 4,870 future cancers, Miglioretti and colleagues reported.
Reducing doses in the highest quartile of doses may prevent 43% of these cancers, the researchers wrote.
Experts believe about a third of CT scans are unneeded, the researchers said. By eliminating unnecessary imaging in addition to reducing the highest doses, about 62% of those future cancers could be prevented, Miglioretti and colleagues wrote.
Efforts to minimize radiation exposure by eliminating unnecessary scans and using the minimal dose necessary to achieve a satisfactory image should remain “a high priority,” Alan R. Schroeder, MD, of the department of pediatrics, Santa Clara Valley Medical Center in San Jose, Calif., and Rita F. Redberg, MD, of the department of medicine and women’s cardiovascular services at the University of California, San Francisco, wrote in an accompanying editorial.
“We can still do more to decrease the use of unnecessary scans — for which the benefit does not outweigh the risk — and to decrease the level of radiation exposure from necessary scans.” Schroeder and Redberg wrote. “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. Uncertainty can be unsettling, but it is a small price to pay for protecting ourselves and our children from thousands of preventable cancers.”
Despite the fact there is clear room for improvement, the current study does contain “good news,” they added.
“Miglioretti et al demonstrate a plateau and then a subsequent small decline in all types of imaging from 2007 to 2010,” Schroeder and Redberg wrote. “Perhaps educational campaigns such as Image Gently are having an effect on physician behavior and parental/patient attitudes. The recent focus on unnecessary imaging in the Choosing Wisely campaign’s ‘top 5’ lists from the American Academy of Pediatrics and the pediatric committee of the Society for Hospital Medicine should help to garner additional momentum on this issue.”