CHILDREN undergoing life-saving CT scans could triple the risk of developing leukaemia and brain tumours, North East scientists have warned.
Research from Newcastle University suggests the use of the 3D X-rays can break-down DNA and damage gene cells to trigger the life-threatening illnesses.
Previously medics have relied on risk estimates drawn from tests on Japanese atomic bomb veterans in the Second World War, which indicated that exposure posed a health risk.
Now scientists in Newcastle have studied data on around 180,000 patients under the age of 22 who had CT scans at UK hospitals between 1985 and 2002.
For the first time, research has proven that exposure to radiation from the low-dose scans can escalate the risk of brain tumours and leukaemia by up to three times.
Last night Dr Mark Pearce, the lead researcher at Newcastle University, said the scans were a “life-saving tool”, but called for “better justification” for the use of the equipment.
Dr Pearce said: “What we’ve been looking at is whether there is a potential cancer risk in children and young adults who have CT scans.
“We’ve found significant increased risks of brain tumours and leukaemia in line with the number of doses of radiation from the scans.
“The scans have been around since the early 1970s, but up until now no one has been able to study this in the way that we have. This is the first study using empirical data.
“What’s important to stress is that the trebling of risk is the trebling of a very small risk. However, it is important that CT scans are only used when justified.”
Dr Pearce started a pilot study eight years ago before examining data from around 180,000 patients from 70 NHS trusts across Britain. Results showed children younger than 15 would receive enough radiation from two to three head CT scans to triple their risk of developing brain cancer.
Because brain and bone marrow do not absorb X-rays at the same rate, academics found that it would take five to 10 head scans to triple the risk of leukaemia. Figures published in The Lancet medical journal showed that the chances of an individual developing cancer after a CT scan remain small.
For children under 10 receiving head scans, around one extra case of leukaemia and one extra brain tumour per 10,000 patients would be expected during the decade after the procedure.
The study did not look at the reasons why children underwent CT scans, but ensured it was not because they already had brain tumours or leukaemia.
Northumberland-based Prof Sir Alan Craft, former president of Royal College of Paediatrics, last night said: “Nobody has ever been able to quantify how risky X-rays are.
“What this study has done is to identify almost 250,000 children across the UK who have had CT scans over the last 25 years and link them to the national register for cancer.
“What we’ve proved is that there is a link between having a CT scan and subsequently getting leukaemia and brain tumours. CT scans are good for you – they identify problems and save lives – but you’ve got to balance the risk of one against the other.
“In this country, the scans are pretty well justified, you don’t get an X-ray for no good reason. That’s not the same in the US where you are five times more likely to get a CT scan.
“The chances of any young person getting leukaemia is one in 200.
“If they’ve had two to three CT scans, it goes down to one in 600. The absolute risk is still small.”
A COMPUTERISED tomography (CT) scanner is a special kind of X-ray machine.
Instead of sending out a single X-ray through your body as with ordinary X-rays, several beams are sent simultaneously from different angles. Beams are detected after they have passed through the body.
Previously it was assumed that low-dose scans posed negligible risks even to children, who are more sensitive to radiation.
But experts acknowledge there are crucial differences between exposure to radiation from an atomic bomb and a medical procedure. CT scans are focused on a region, such as the head, rather than the whole body.
Prof Richard Wakeford, from the Dalton Nuclear Institute at the University of Manchester, said: "As with all sources of radiation exposure, this small risk should be taken into account when radiation is used."