RADIATION FROM two or three CT scans of the head in children under 15 can triple their risk of later developing brain cancer, a study published today has found.
However the “absolute risk” of developing these “relatively rare” cancers after a CT (computed tomography) scan were “small”, authors of the UK-based study in the Lancet said.
The risk of developing leukaemia was also tripled after children aged under 15 had between five and 10 CT scans of the head, the study found.
A decade after a child under 10 received its first CT scan of the head there was one extra case per 10,000 scans for both leukaemia and brain cancer, the authors estimated.
The study looked at CT scans of almost 180,000 patients aged under 22 which were undertaken in the UK between 1985 and 2002. It followed patients for later cancer diagnosis.
The study focused on the different rates of absorption of radiation by the brain and bone marrow from CT scans on a variety of body parts such as abdomen, chest and head. It ruled out scans on children with existing brain tumours or leukaemia.
It is the first study to provide direct evidence of a link between exposure to radiation from CT in childhood and cancer risk, the authors said.
The use of CT scans has risen sharply in the past decade. The scans produce 3D X-ray images. It has wide application including for diagnoses of bone disorders, brain tumours and internal organ injuries.
The clinical benefits of CT scans outweighed the absolute risk, lead author Dr Mark Pearce of Newcastle University said. He recommended that radiation dosage in CT scans be kept “as low as possible” and alternative procedures not using ionising radiation (such as MRI or ultrasound) “should be considered” if appropriate.
“Of utmost importance is that where CT is used, it is only used where fully justified from a clinical perspective,” Dr Pearce said.
Further refinements to allow the reduction in CT doses should be prioritised by radiologists and manufacturers, he added.
Dr Pearce recommended the continued “widespread use” of CTs which could remove the need for anaesthesia in young patients.
A CT scan is a “really important and integral part of managing acutely ill children,” Prof Alf Nicholson, a consultant paediatrician at Temple Street hospital, Dublin, said of the headline findings.
CT scans should be used “judiciously” and there was a balance between having a scan and the risk of delaying a scan, he said. The risk from a head CT scan was “very slight” and brain cancer was a “rare event”. It was the only way to diagnose certain brain conditions but scanning for headaches on a mass basis was “not a good idea”.
