London: Kids who undergo two or more head CT scans have triple the risk of developing brain cancer, a new study has revealed.
According to the first large-scale study, children having multiple CT scans are also at greater risk of leukaemia.
Researchers estimate that for every 10,000 head CT scans given to children aged ten years or younger, one more case of leukaemia and one more brain tumour would be diagnosed as a result.
But they said that CT scans are lifesaving and the absolute risk of developing cancer is very small.
They also said restrictions on their use in the UK mean doctors are more cautious about giving children CT scans than in other countries.
“CT scans are accurate and fast, so they should be used when their immediate benefits outweigh the long-term risks,” the Daily Mail quoted Dr Mark Pearce, lead author of the study from Newcastle University, as saying.
“We have now shown that they increase the risk of cancer, but these are rare diseases. It’s a tripling of a small risk, but we have to still be aware that any risk is a risk,” she said.
In the study researchers from Newcastle University and the National Cancer Institute in the US looked at 175,000 children and young people under 21 being treated on the NHS who received their first CT scan between 1985 and 2002.
They estimated the amount of radiation received at different sites in the body and found a link between the dose and the risk of brain tumours and leukaemia over the next ten years.
The risk of brain tumours rose threefold after an absorbed dose to the head of 50 to 60 milligray – a unit of absorbed radiation. This is an exposure level of around two to three head CT scans.
The same dose to bone marrow would be produced by five to ten head CT scans, which would triple the risk of leukaemia.
A Department of Health spokesman said CT scans were carried out only when ‘clinically justified’. Cancer rates in those aged up to 19 are three brain tumours and 4.5 leukaemia cases per 100,000 people.
The study has been published in The Lancet.