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Lifetime cancer risk from imaging radiation low in most pediatric heart patients
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The cumulative radiation exposure incurred through imaging tests is relatively low and does not significantly increase the lifetime risk for cancer among most children with heart disease, according to recent findings.
However, some pediatric patients with more complicated disease are exposed to higher cumulative doses of radiation and may face an up to 6.5% increase in lifetime cancer risk, the researchers wrote. Additionally, female patients have a higher lifetime risk than males.
Researchers evaluated 337 patients with heart disease aged 6 years or younger who underwent surgery at a single hospital from July 2005 to 2010. All patients underwent one of the following surgeries: isolated atrial septal defect closure; isolated ventricular septal defect closure; atrioventricular canal defect repair; tetralogy of Fallot repair; isolated arterial switch operation; cardiac transplantation; or Norwood operation.
The researchers collected data on all radiation exposure from birth in each patient and documented the specific imaging modalities used. The patients were exposed to 13,932 examinations involving radiation, 92% of which were conventional radiographs.
Although conventional radiographic examination accounted for 92% of all examinations performed, they were linked to only 8% of the cumulative dose. In contrast, 1.5% of examinations were cardiac catheterization procedures, which contributed 60% of total exposure.
Researchers estimated radiation dose according to the targeted organ system and used this quantification to approximate the effective dose. They determined the cumulative cancer risk, as well as gender- and age-specific lifetime attributable risk of cancer, based on the effective dose.
The overall median cumulative effective dose was 2.7 mSv (range, 0.1 mSv-76.9 mSv), with a lifetime attributable risk for cancer of 0.07% (range, 0.001%-6.5%). However, the researchers observed significant variations in the lifetime attributable risk for cancer according to the extent of surgical complexity, with more than 350 cases per 100,000 children who underwent CT chest angiography vs. 0.2 cases per 100,000 patients who underwent portable chest X-ray.
The lifetime attributable risk for cancer per unit of exposure was twice as high among female patients (0.04% per 1-mSv effective dose for females vs. 0.02% per 1-mSv effective dose for males; P<.001). The researchers attributed this gender disparity to increased risk for breast and thyroid cancer among female patients.
The researchers concluded that health care providers should aim to reduce radiation exposure among high-risk cohorts, including females and those who would require repeated, high-exposure imaging.
“There are definitely times when radiation is necessary,” researcher Kevin Hill, MD, cardiologist and assistant professor of pediatrics in the cardiology division at Duke University School of Medicine, said in a press release. “But it’s important for parents to ask and compare, in case you can avert potentially high-exposure procedures. Often, there are alternative or modified procedures with less radiation, or imaging may not actually be necessary.”
Disclosure: One researcher reported receiving support from the US Nuclear Regulatory Commission and the US Department of Energy, as well as from a Coulter research grant from Duke University for his work on radiation dosimetry.
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