Slight Risk of Cancer From CT Scans

Leukemia or brain cancer risk from childhood CT scan is 1 per 10000

(RxWiki News) While the amount of radiation from an X-ray is not very much, a CT scan is a collection of a few dozen X-rays in a quick series, and it begins to add up.

As a recent study points out, some caution is necessary to protect children, who have more developing cells that are vulnerable to radiation. Emergency physicians generally try to avoid using CT scans on children unless absolutely necessary, and recent research supports their position.

Conclusions from the joint study between the United States' National Cancer Institute and the Institute of Health and Society in England found that the risk of leukemia or brain tumors increased after CT scans were used.

"Don't insist on CT scan if your doctor doesn't think it's necessary."

Researchers quickly pointed out that the risks of missing an important problem revealed by repeated X-rays of the head far outweighed the slight increase in cancer risk, which is estimated to be no more than one case per 10,000 CT scans.

While it's true that children are more sensitive to radiation, signs of internal bleeding can be easy to miss until it's too late.

This study does not show any evidence for refusing a CT scan in an emergency situation, but the risk should be taken into account by medical professionals now that CT scans are beginning to be used for screening purposes.

The lead author of the study, Mark Pearce, PhD, from the United Kingdom's Newcastle University stated,"The immediate benefits of CT outweigh the potential long¬term risks in many settings and because of CT's diagnostic accuracy and speed of scanning, should remain in widespread practice for the foreseeable future."

"Alternative diagnostic procedures that do not involve ionizing radiation exposure, such as ultrasound and MRI might be appropriate in some clinical settings. [When] CT is used, [should] only be used where fully justified from a clinical perspective."

Amy Berrington de González, PhD and one of the study authors from the National Cancer Insitute added,"It's well known that radiation can cause cancer but there is an ongoing scientific debate about whether relatively low doses of radiation like those received from CT scans do increase cancer risks, and if so the magnitude of those risks. "

"Ours is the first study to provide direct evidence of a link between exposure to radiation from CT in childhood and cancer risk and we were also able to quantify that risk."

The study reviewed patient data on CT scans at British National Health Service hospitals between 1985 and 2002, nearly 180,000 pediatric head CT scans.

Out of that patient population, 74 were later diagnosed with leukaemia and 135 with brain tumors within the next ten years.

After statistically analyzing the data and accounting for the natural incidence of both cancers, researchers concluded that the increase in cancer risk was very slight, 1 new case per 10,000 children given a head CT scan.

Researchers mentioned that the tighter regulations in the United Kingdom require doctors to document the necessary nature of scans that use ionizing radiation, were invaluable in providing researchers with enough data.

As a side note, radiation is part of everyday life, and ionizing radiation received during a plane from Los Angeles to New York is equivalent to the radiation from two chest x-rays.

For more perspective, it would take 25 CT scans of the head to reach the limit established by the United States as the maximum acceptable level for nuclear power plant workers per year.

Both brain tumors and leukemias in children remain relatively rare, and the lack of a surge in incidence since the widespread use of CT scans began supports the conclusions of the authors that an acceptable level of risk is involved for emergency imaging in children.

The study was published in The Lancet on June 7th, 2012.

Funding for the study was provided by the US National Cancer Institute and UK Department of Health.

Review Date: 
June 8, 2012