Health. Medical imaging: Radiation causes 10% of blood cancers in children

Is radiation from medical imaging the cause of 10% of blood cancers in children? This is what a study from the University of California, San Francisco (UCSF) and the University of Davis suggests, published in the New England Journal of Medicine on September 17.

The researchers examined data from nearly 4 million children and adolescents born between 1996 and 2016 in the United States and Canada. They were then able to quantify the link between exposure to radiation (a known carcinogen) from medical imaging and hematological cancers—particularly leukemia and lymphoma, which are the most common cancers in this age group.

The scanner, particularly at risk

According to the results, one in ten blood cancers is attributable to medical imaging, or nearly 3,000 in total over the period studied, including 79.3% lymphoid malignant blood diseases, 15.5% myeloid malignant blood diseases and acute leukemia.

The risk increased proportionally with the amount of radiation the children received. In addition, the risks were higher for high-dose medical imaging tests, such as computed tomography (CT) scans.

X-rays, on the other hand, expose children to much lower doses. For example, one or two head scans were associated with a 1.8-fold increased risk of cancer diagnosis, and this risk was 3.5 times higher for children who had more scans and therefore were exposed to more radiation. In contrast, for those who had one X-ray, they estimated that only a small fraction of subsequent cancers were associated with radiation exposure.

Why are children particularly at risk?

Because this exposure is cumulative, individuals, particularly children, who undergo multiple low-dose or multiple high-dose scans may be exposed. Children are at greater risk because they live a long time after exposure, allowing time for cancer to develop. Indeed, an adult has a lower risk of cancer after exposure because of their shorter lifespan. In addition, children's cells divide more rapidly and are more at risk of radiation damage.

"Children are particularly vulnerable to radiation-induced cancer due to their increased radiosensitivity and longer life expectancy ," said Rebecca Smith-Bindman, a radiologist and professor of epidemiology at UCSF and lead author of the study, quoted in a press release. "While medical imaging can save lives, our findings underscore the critical importance of carefully evaluating it and minimizing radiation exposure during pediatric imaging to preserve children's long-term health."

The authors therefore recommend using irradiating imaging only when it provides essential information for the child's care and, in the case of computed tomography, applying the lowest possible radiation doses. According to them, ultrasound and MRI, non-ionizing imaging techniques, could be used in many cases without compromising the diagnosis.