Newcastle University: Increased cancer risk from CT scans

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The amount of radiation used in CT scanners is carefully measured for each patient. Photo: ITV

Researchers at Newcastle University claim children and young adults scanned multiple times by computed tomography (CT), a commonly used diagnostic tool, have an increased risk of leukaemia and brain tumours in the decade following their first scan.

“This is the first direct evidence of a link between exposure to radiation from CT and cancer risk in children. While the risks are small, the medical community needs to consider carefully its use of CT scans and

refine their use as a priority. We need to look at worldwide regulation.

– Dr Mark Pearce, Newcastle University

The findings, published online today in The Lancet, from a study of more than 175,000 children and young adults was led by researchers at Newcastle University and at the National Cancer Institute, part of the National Institutes of Health, USA. The researchers emphasise that when a child suffers a major head injury or develops a life-threatening illness, the benefits of clinically appropriate CT scans should outweigh future cancer risks.

CT imaging is said to be a vital diagnostic technique and it is used more frequently in countries such as the USA and Japan. However, CT scans deliver a dose of ionising radiation to the body part being scanned and to nearby tissues. Even at relatively low doses, ionising radiation can break the chemical bonds in DNA, causing damage to genes that may increase a person’s risk of developing cancer. Researchers say children typically face a higher risk of cancer from ionising radiation exposure than do adults exposed to similar doses.

CT scan
An image showing a cross-section of a male stomach Credit: Newcastle RVI

In the study, the researchers estimate that for every 10,000 head CT scans performed on children 10 years old or younger, one more case of leukaemia and one more brain tumour would occur than would normally be expected.

The investigators obtained CT examination records from radiology departments in hospitals across Britain and linked them to data on cancer diagnoses and deaths. The study included people who underwent CT scans at British National Health Service hospitals from birth to 22 years of age between 1985 and 2002.

Information on cancer incidence and mortality from 1985 through 2008 was obtained from the National Health Service Central Registry, a national database of cancer registrations, deaths and emigrations.