Children receiving several CT scans are at higher risk for brain tumours and leukemia, says a new study out of the UK. This is the first study to show a direct link between multiple CT scans and cancer risk.
In children, CT scans are used mostly to look at the head, neck or spine, when trying to diagnose injury or neurological disorders. This type of imaging, while useful, has higher doses of radiation than X-rays.
Researchers at Newcastle University in the UK evaluated almost 180,000 young people (under age 22) who underwent CT scanning in the UK between 1985 and 2002. These patients were followed until 2008.
While the study included CT scans from all parts of the body, most scans were of the head. Researchers actually studied the radiation doses from the scans rather than the number of scans. This is because the amount of radiation a child receives from CT depends on their age, size, and which body part is being scanned.
By 2008, 74 young people in the study developed leukemia and 135 had brain tumours.
Taking the amount of radiation usually received from a CT scan into consideration, the researchers concluded that a child's risk of brain tumour triples after having two to three scans. The risk of leukemia triples with five to 10 CT scans. To put that into context, the average child's risk of leukemia is one in 2000; after having several CT scans, their risk increases to one in 600.
The researchers were quick to point out that brain tumours and leukemia are rare conditions and the risk, while increased after having multiple CT scans, still remains low.
"As long as a CT is clinically justified, the benefits will almost always outweigh the risks. The risks are small, despite the increase with increasing dose. We hope that our findings reinforce the concept that CT scans should only be done when clinically justified, so if a parent is really concerned, they can ask for confirmation of this. But we hope our findings also reassure parents about the small risks involved," said lead researcher Dr. Mark Pearce of Newcastle University, in an email interview with Digital Journal.
The use of CT scans has increased in the last three decades, and people are five times more likely to have a CT in the US compared to the UK. There is no evidence to suggest that CT scans are being overused, said Dr. Pearce; however, "in Europe, we have regulations that state that any CT must be clinically justified, so this may explain differences in usage rates between countries."
The American College of Radiology (ACR) is urging parents to discuss the risks and benefits of CT with their physician and factor this discussion into their decision-making before a scan is performed. If the scan is warranted, the immediate benefits outweigh the very small long-term risk of cancer.
The website also suggests parents keep track of their child's X-ray history and ask the following questions before having a CT scan:
• How will having this exam improve my child’s health care?
• Are there alternatives that do not use radiation which are equally as good?
• Will my child receive a “kid-size” radiation dose?