New research is offering clarification on cancer risks associated with radiation exposure from medical imaging conducted during childhood.  

After analyzing the cases of nearly 8,000 young adults (less than 25 years old) diagnosed with intracranial tumors, leukemia or lymphoma and their history of medical imaging alongside that of almost 80,000 matched controls, experts concluded that a single CT scan does not increase a child’s risk of later developing cancer. However, children who undergo repeated CT scans before the age of 6 face almost double the risk. 

These findings were shared recently in the Canadian Medical Association Journal. 

"Our work reinforces the importance of radiation protection strategies, addressed by the International Atomic Energy Agency," study designer Yu-Hsuan Joni Shao, with the College of Medical Science and Technology at Taipei Medical University in Taiwan, and co-authors suggested. "Unnecessary CT scans should be avoided, and special attention should be paid to patients who require repeated CT scans." 

Specifically, the team found that children who undergo four or more CT scans before the age of 6 have the highest risk (2.3-fold increase) of later developing intracranial tumors, leukemia and non-Hodgkin lymphoma compared to those with no ionizing radiation exposure. Children of the same age with 2 to 3 exposures face increased risk of intracranial tumors, while just one exposure was not found to be associated with adverse diagnoses. 

The authors acknowledged that these cancers remain uncommon while adding that their study also had limitations, including a low sample size of children who had undergone repeated CT scans. For this reason, they suggested that their findings “should be interpreted cautiously, as the risks may be overestimated because of residual confounding and the low number of participants in high-radiation groups.” 

Nonetheless, they suggested that their findings also reiterate “the importance of prudent use of CT in the pediatric population,” and encourage parents to have informed discussions with their child’s provider about the risks versus benefits of medical imaging that utilizes ionizing radiation. 

The study can be viewed here.