EPI-CT: European cohort study of cancer risk after paediatric computed tomography

The long-term risk of radiation induced cancer or other health effects following computed tomography (CT) scanning has never been directly assessed. There is scientific evidence that radiation exposures

• down to about 100 mSv in adults and
• down to about 10 mSv in children

can cause cancer. However, even below these levels of proven effects, increased cancer risks due to radiation exposure have to be assumed.

The worldwide increasing use of paediatric computed tomography (CT) raises the question of possible late effects, caused by exposure to ionising radiation.

International cohort study

The European collaborative EPI-CT project was the first large-scale cohort study to investigate cancer risks and the underlying biological effects induced by medical CT exposure. It aimed at studying the cancer risks and the underlying biological effects in an international cohort study with more than 1 million children participating. The project ended on 31^stJanuary 2017, the final report is prepared.

The project was coordinated by the Section of Environment and Radiation at the International Agency for Research on Cancer (IARC). Eighteen centres from

• Belgium,
• Denmark,
• Germany,
• Finland,
• France,
• Luxemburg,
• the Netherlands,
• Norway,
• Spain,
• Sweden and the
• United Kingdom

cooperated in this project.

The cohort populations were assembled both, retrospectively and prospectively until 2013. For each child in the cohort, organ specific dose estimates were derived based on Monte Carlo computer simulation of radiation exposure in the human body by using hybrid mathematical phantoms of children of various ages. Linkage with national cancer registries allowed to calculate cancer incidence in the pooled cohort and to perform external comparisons (SIR-analysis). Association between estimated organ dose and cancer incidence was evaluated. In parallel, biomarkers of CT exposure and age dependent sensitivity to radiation were tested in blood and saliva.

Powerful study of paediatric CT scans

EPI-CT should provide direct epidemiological evidence on the potential cancer risk due to low doses of ionising radiation exposure in a large multinational European cohort. It is the largest, and the statistically most powerful study of paediatric CT scans undertaken until to date.

Results will contribute to

• radiation protection,
• dose optimisation of CT scans and
• low dose radiation research.

This project was supported by the EU FP7 Euratom grant agreement n°269912.

BfS investigated age dependent radiosensitivity in a feasibility study

In this project the BfS organized a feasibility study to investigate age dependent radiosensitivity. Together with clinical partners in Munich (LMU, TUM), blood samples from three age groups ranging from newborns (umberical cord blood), young children (2 – 5 years) to adolescents were collected in 2011 and 2012 and investigated for different DNA damage parameters. Blood samples were irradiated in a CT scanner in vitro and chromosome aberrations as well as the induction and repair of DNA double strand breaks using γ H2AX foci were analysed. In vitro irradiated blood cells of newborns and young children showed a 1.5-fold increased rate of chromosome aberrations compared to adults.

The ethics committee of the “Bayerische Landesärztekammer” approved the current project. Informed consent was sought from every participant or its parents/care takers before taken blood samples.

The results will be used to access the feasibility of conducting a larger study with enough power to further estimate age and sex dependent radiosensitivity.