Lifetime cancer risk from heart imaging is low for most children, but more complex tests raise risk

Radiation from standard X-rays is relatively low and doesn’t significantly raise lifetime cancer risks for most young children, according to a recent paper (Johnson et al. Cumulative Radiation Exposure and Cancer Risk Estimation in Children with Heart Disease. Circulation 2014 Jun 9.113.005425) from Duke University Medical Center in Durham, NC USA. The researchers followed 337 children under age 6 who had had surgery for heart disease. Their operations required almost 14,000 imaging procedures, including X-rays, CT scans, and cardiac catheterization using fluoroscopy.

The study is the first in which researchers quantified cumulative radiation doses in pediatric  heart patients and predicted lifetime cancer risks based on the type of exposure. The researchers found that for the average child in the study, the cumulative effective dose of ionizing radiation was relatively low — less than the annual background radiation exposure. However, some children with complex heart disease can be exposed to large cumulative doses that increase the estimated lifetime risk of cancer up to 6.5 percent above baseline.“There are definitely times when radiation is necessary,” said Dr Hill study lead author “But it’s important for parents to ask and compare in case they can avert potentially high exposure procedures. Often, there are alternative or modified procedures with less radiation, or imaging itself may not actually be necessary.”

In the study, the researchers reviewed medical records to find the most common imaging procedures, calculated how much radiation the organs absorbed during each procedure, then used a US National Academy of Sciences report to analyze lifetime cancer risks based on the amounts of exposure. The study results showed that although X-rays accounted for 92 percent of imaging exams,  81 percent of the overall radiation exposure was a result of cardiac catheterizations and CT scans. Overall, lifetime cancer risk was found to increase from 0.002 percent for chest X-rays to 0.4 percent for complex CT scans and cardiac catheterization. Because they are more prone to breast and thyroid cancers, girls have double the cancer risks of boys.