International study on CT scans and leukaemia risks in children

Source: Tyler Olson/Stock.adobe.com

Computed tomography (CT) is an important tool for the medical diagnosis of patients but is generally associated with a higher radiation dose than conventional X-ray examinations.

A year ago, the International Agency for Research on Cancer (IARC) already published results relating to brain tumour risk following CT scans of the head. These are now joined by results relating to cancers of the haematopoietic system (haematological cancers), such as leukaemia and lymphomas. This work is part of the world's largest study of radiation risk due to CT scans in childhood and adolescence, known as the Epi-CT cohort study.

Published in November in the journal "Nature Medicine", the study reveals significant correlations between CT-related radiation exposure and an increased risk of leukaemia and lymphomas. It included around 877,000 children and adolescents who underwent CT scans. In subsequent years, 790 haematological cancers occurred within this group.

For the risk assessment as part of their work, the scientists first determined the individual dose received by the red bone marrow from each CT scan. They demonstrated a statistically significant increase in risk at radiation doses for the red bone marrow of over 10 milligrays (mGy), as well as an increase in risk with increasing dose.

On average, a modern CT scan leads to a dose of some 8 mGy, resulting in a 16 % increase in risk according to the results of the study. Based on these figures, it can be assumed that there will be 1.4 additional cases of cancer per 10,000 examined children and adolescents within 12 years of a scan.

In Germany, around 110,000 CT scans are carried out each year on children and adolescents under the age of 20. In the inpatient area, the number of examinations for children under 15 has fallen significantly since 2007. Each year, a total of around 1,100 children and adolescents under 18 develop haematological cancers.

The results of the study represent a key contribution to assessing the risks associated with small radiation doses. The data supports the approach of consistent dose reduction in radiological examinations, which has been pursued in Germany for several years. Moreover, it underpins the importance of the principles of radiation protection in medicine. In principle, CT scans are only appropriate when there is a clear indication for their use. For children and young people, care is taken to ensure a particularly narrow interpretation of this "justifying indication".