In a largest-of-its-kind study published in the journal Circulation, researchers quantified cumulative radiation doses in 337 pediatric heart patients and predicted lifetime cancer risks based on exposure levels.
Researchers found that the average child in the study had a low risk based on their cumulative dose, which was lower than the average background exposure in the United States. Children with complex heart disease, however, had an elevated cancer risk 6.5 percent above baseline.
A multidisciplinary team at Duke University Medical Center (including prominent pediatric radiologist Donald Frush, MD), looked at children 6 years of age or younger who had undergone one of seven primary surgical procedures for heart disease between 2005 and 2010: isolated atrial septal defect closure, isolated ventricular septal defect closure, atrioventricular canal defect repair, tetralogy of Fallot repair, isolated arterial switch operation, cardiac transplantation, and Norwood operation. The surgeries selected were common and represented a range of complexity.
Radiation exposure data was collected from birth, including all examinations performed with radiation-producing imaging modalities. The median age at surgery for the entire cohort was 88 days. Data were collated by searching institutional databases and CPT codes through the EHR, with chart reviews performed on 10 percent of the patients to confirm the search accuracy.
Organ-specific doses were measured for all conventional angiographic projections using phantoms representing 1 and 5 years of age and incorporating dosimeters within cancer susceptible tissue structures. Fluoroscopy assessment was based on the pulsed frame rate of 15 frames per second, and the cineangiography was 30 frames per second. The researchers then developed a proprietary radiation dose calculator to determine total catheterization effective dose.
For all other radiographic examinations, age-specific effective-dose estimates were obtained from previously published institutional data and from the peer-reviewed radiology literature.
The researchers estimated age- and sex-specific lifetime attributable risk (LAR) of cancer using the approach of the National Academy of Sciences Committee on Biological Effects of Radiation (BEIR) VII. Because they are more prone to breast and thyroid cancers, female pediatric patients have twice the risk of their male counterparts.
Not surprisingly, the team found that catheterization and chest CT are the most significant contributors to cumulative radiation dose and lifetime cancer risk. “These data provide actionable information that could be used to reduce exposure and suggest that the greatest risk reduction can be achieved with a targeted approach focused on minimizing radiation use during high exposure examinations such as catheterization and CT,” the team wrote.
Cumulative effective dose for the overall patient cohort was relatively low, with the exception of children with complex heart disease. For these patients, the research team recommend using the relative exposure estimates shared in their article when choosing between various radiation-emitting imaging modalities.
“With a burgeoning population of children with heart disease surviving into adulthood, these advances will have a very meaningful public health impact,” they conclude.