Brain cancer after radiation in connection with CT examinations of children and adolescents

The Cancer Registry of Norway has participated in a European study investigating the incidence of brain cancer among children and adolescents who have undergone CT scans.

The article is published in The Lancet Oncology, and shows a significant correlation between increasing radiation dose and the risk of brain cancer, and emphasizes the importance of CT scans being performed on a good medical indication and carried out so that radiation is reduced as much as possible.

CT scans provide invaluable, sometimes life-saving, diagnostic information. At the same time, patients are exposed to much higher radiation doses than with X-ray examinations or other radiological procedures.

Large amounts of data

Data from a total of 658 752 children and adolescents who have undergone one or more CT scans were analysed. The analyses showed that for every 10,000 children who had a CT scan of their head, one radiation-related case of brain cancer would be expected during 5-15 years of follow-up.

The study is part of the European EPI-CT cohort study, which is coordinated by IARC, and so far the largest international study of cancer risk among children and adolescents who have undergone CT scans. In total, approximately one million children from 276 hospitals in nine European countries are included.

Individual radiation doses were reconstructed using historical machine parameters and a large selection of CT images. Information about the individual participants was linked to information from cancer registries in the participating countries. The results showed a statistically significant linear dose-response in the context of brain cancer. Excess relative risk (ERR) per 100 milligray radiation dose to the brain was 1.27 (95% confidence interval 0.51, 2.69).

It is a challenge to analyse and interpret cancer risk related to CT scans among children because (a) randomised data are not available, (b) cancer among children is rare and therefore very large studies are required, and (c) the medical reason why the CT scan was performed may in itself affect the risk. A number of sensitivity analyses were conducted, and it was concluded that it is unlikely that the observed associations could be explained by such factors.

The risk observed in the study is small. At the population level, the results are nevertheless important, because every year there are very many children and adolescents who undergo CT scans of the head. The results underline the necessity of good radiation protection in medical practice to ensure that this valuable diagnostic procedure is used as appropriately as possible.

The study can be found here