X-rays: 4 or more scans before age 18 increase the risk of certain cancers

2023-04-25 11:44:49

X-ray exposure during childhood would not be so trivial as that, at least if we are to believe a new scientific study.

Published this April 24, 2023 in the Canadian Medical Association Journal (Source 1), a scientific study indeed indicates that if a single scanner is first safe in terms of carcinogenic risk, exposure to 4 or more scans before the age of 18 would more than double the risk of brain tumour, leukemia or lymphoma.

To reach this disturbing conclusion, the research team looked at data from 7,807 Taiwanese children who were diagnosed with an intracranial tumor, leukemia or lymphoma between January 1, 2000 and December 31, 2013. Data that was compared to those of 78,057 “control” children, who had not received such diagnoses.

The team was thus able to observe that having spent a computed tomography (Also called CT-scanner or simply scanner) was not associated with an increased risk of these cancers, compared to no CT scan during childhood. In contrast, children who had 2 to 3 scans had an increased risk of intracranial tumors, and those who had 4 or more had a more than doubled risk of intracranial tumors, leukemia and non-Hodgkin’s lymphoma. note that youngest exposed children X-rays were all the more at risk of developing these cancers: “receiving 4 or more CT scans at age 6 or earlier was associated with the highest cancer risks, followed by [tranches d’âges] from 7 to 12 years old and from 13 to 18 years old”, say the authors.

“Our work strengthens the importance of radiation protection strategiesaddressed by the International Atomic Energy Agency”, said Dr Yu-Hsuan Joni Shao, researcher at Taipei Medical University (Taiwan), and co-author of the study. He estimates that “unnecessary CT scans should be avoided and special consideration should be given to patients who require repeat CT scans”.

Scientists conclude that “parents and [jeunes patients] should be well informed about the risks and benefits prior to radiological procedures and encouraged to participate in decision-making regarding imaging”.

What about in France?

In France, the Institute for Radiation Protection and Nuclear Safety (IRSN) estimates that “the doses of ionizing radiation delivered by a scanner remain in the range of so-called “low” doses for medical exposures”. The IRSN specifies that the dose received during a scanner is nevertheless equivalent to approximately 3 years of exposure to natural radioactivity and it is significantly greater than that of a conventional X-ray (100 times more for example for a CT scan of the thorax compared to a simple chest X-ray).

In 2022, she gave the results of the EPI-CT study, a European epidemiological study carried out to estimate the risk of cancer following scans during childhood. This had shown that, even if the risk ist low with regard to the diagnostic benefitthere is indeed “an excess risk of developing a malignant brain tumor after CT examinations of the head in children and young adults”.

These results had, according to the IRSN, confirmed the importance and usefulness of the mandatory principles of radiation protection already in force, particularly with regard to the risk-benefit ratio. These rules include three main principles: justification (is the examination justified and essential?), substitution (can the examination be replaced by another without X-rays, such as MRI or ultrasound?) and optimisation (use the lowest possible dose while maintaining the best possible examination quality).