The estimated 4 million computed tomography (CT) scans that are given each year to children under the age of 15 in the United States result in almost 5,000 future cases of cancer, according to a study published Monday in the journal JAMA Pediatrics.
In girls, about two-thirds of those CT-related cancers will be cases of leukemia or tumors of the breast, thyroid or lung, according to the study’s projections. In boys, about half of the future cancers will be cases of leukemia or tumors of the brain, lung and colon.
The researchers project, for example, that for every 300 to 390 girls who undergo an abdomen/pelvis CT scan, one will develop a cancer. They also estimate that 1 in 500 abdomen/pelvis scans may result in a future cancer death.
Those cancers could be reduced by a dramatic 62 percent, the authors of the study add, if CT scans were used only when medically necessary and if dose-reduction strategies, similar to ones already in place in Europe, were implemented.
The researchers, which analyzed patient data records from seven large U.S. health-care systems, also report substantial variation among medical institutions in the radiation doses used in the CT imaging of children.
Many children in the study received radiation doses of 20 millisieverts (mSv) or higher for a single CT scan. In Europe, 20 mSv is the yearly limit of exposure permitted for people who work with radiation, the researchers point out.
“We found that many children received high radiation doses from CT associated with a small but significant increase in future cancer risk,” they conclude. “This is due to both the greater use of higher-dose CT types, such as abdomen and pelvis scans, and the wide variability in radiation doses delivered for each examination.”
Up to 500 times more radiation than X-rays
CT scans, which generate cross-sectional images of the bones and soft tissues in the body, deliver ionizing radiation doses that are 100 to 500 times higher than conventional X-rays. This is of particular concern for children because their smaller bodies tend to absorb more radiation and because the cells in their still-growing bodies are dividing rapidly. Both are factors that increase their risk of developing radiation-induced cancer.
Although CT scans can, of course, be lifesaving diagnostic tools in certain situations, they are often overused, say the study’s authors. Other, safer imaging technologies, such as magnetic-resonance imaging (MRI) and ultrasound, will frequently work just as effectively.
The use of CT scans has increased dramatically during in recent years. The current study found that CT imaging doubled among children under the age of 5 and tripled among children aged 5 to 14 between 1996 and 2005. The rate then stabilized for a couple of years before starting to decline in 2008. The authors attribute this decline at least partially to the 2007 launch of the Image Gently campaign, an initiative of the Alliance for Radiation Safety in Pediatric Imaging that has raised awareness about the need to reduce children’s exposure to unnecessary radiation.
In December 2012, the Minnesota Department of Health because the first state health agency in the country to endorse the Image Gently campaign and its twin initiative for adults, the Image Wisely campaign.
What parents can do
“Parents can be educated about [radiation imaging] risks by being encouraged to ask not only what a proposed imaging test is intended to detect but, more importantly, how such detection would help their children,” write Dr. Alan Schroeder, a pediatrician at the Santa Clara Valley Medical Center in San Jose, Calif., and Dr. Rita Redberg, a cardiologist at the University of California, San Francisco, in an editorial that accompanies the study. “The Image Gently campaign deserves much credit for empowering parents to ask these types of questions. This campaign’s website also encourages parents to use their downloadable ‘My Child’s Medical Imaging Record’ card to track the number and types of imaging studies performed on their child, which should further enable parents to advocate for the limitation of radiation exposure.”
But the responsibility shouldn’t fall only on parents. The ultimate responsibility for developing dose-reduction strategies for children lies within the radiology community, stress Schroeder and Redberg, and the responsibility for eliminating unnecessary CT imaging is the physician’s obligation — although “the family can play a role.”
“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,” they add. “Uncertainty can be unsettling, but it is a small price to pay for protecting ourselves and our children from thousands of preventable cancers.”
The study, which was funded by the National Cancer Institute, and the accompanying editorial are, unfortunately, behind a paywall. Parents who want to learn more about protecting their children from unnecessary or too-high doses of medical-related radiation, can go to the “Parent” section of the Image Gently website.