Child's risk of brain cancer triples after just two CT scans Research suggests that children would also be susceptible to leukaemia
00:58 GMT, 7 June 2012
The risk of brain cancer is tripled in children having two or three head CT scans, say scientists.
Children having multiple CT scans are also at greater risk of leukaemia, according to the first large-scale study.
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.
Children who have multiple CT scans are also at greater risk of leukaemia
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.
Lead author Dr Mark Pearce, reader in lifecourse epidemiology at Newcastle University, said: ‘CT scans are accurate and fast, so they should be used when their immediate benefits outweigh the long-term risks.
'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.’
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
In the study, published in The Lancet, 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.