When the body is sick, sometimes only the computer tomography (CT) is left to find the cause: The body is then x-rayed. The usefulness of the procedure in diagnostics is undisputed. But it is also clear that excessive amounts of radiation increase the risk Cancer to get sick. For this reason, doctors do not order a CT scan lightly.
Now, for the first time, a large-scale international study is measuring how great the risk is Children fails to develop blood cancer as a result of a CT scan. Like the EPI-CT consortium in the specialist journal Nature Medicine writes, data from almost 900,000 people who had at least one CT scan before their 22nd birthday were included in the study. 790 of them developed blood cancer. According to the researchers, the results show “a clear connection” between the dose of radiation to the bone marrow and the risk of developing a form of blood cancer.
A dose of 100 milligrays increased the risk of developing blood cancer by a factor of 3. The unit milligray (mGy) indicates how much energy body tissue absorbs while exposed to a radiation source. During a normal examination today, the bone marrow absorbs an average dose of around eight mGy; This increases the risk of blood cancer in children by around 16 percent. This means that for every 10,000 children who undergo a CT scan, one or two of them can be expected to develop a form of blood cancer within 12 years of a CT scan.
Children are more sensitive to radiation than adults
The EPI-CT project was coordinated by the World Health Organization’s cancer agency IARC and funded by the EU. Epidemiological studies have repeatedly shown that children are more sensitive to radiation than adults. On the one hand, the developing tissue is more susceptible to radiation damage, and on the other hand, the long life span of children that lies ahead increases the overall risk of becoming ill due to radiation. The consequences of low doses of radiation only appear, if at all, many years after exposure. For this reason, only those diseases that occurred two years after a CT examination were included in the EPI-CT analysis. Last year the group had published a data analysis on the connection between CT examinations and brain tumors in children. Accordingly, one in 10,000 children who were examined by CT at least once can be expected to develop a brain tumor in the following five to fifteen years.
Researchers who were not involved in the study praised the new study. It makes a valuable contribution to existing knowledge, says Malcolm Sperrin from the Institute of Physics and Engineering in Medicine (IPEM) in York, England. However, the calculated risk is no higher than previously assumed. This risk must be seen in the context of the diagnostic benefits of imaging procedures, says Sarah McQuaid from IPEM. A medical scan can only be justified if the benefits outweigh the potential risks. Like the EPI-CT group, it also emphasizes how important it is to set the radiation dose as low as possible. “Continuous efforts in this area can reduce the risks even further.”
In Germany, the use of CT in children and adolescents is already “quite restrictive,” says Hajo Zeeb, head of the Prevention and Evaluation Department at the Leibniz Institute for Prevention Research and Epidemiology (BIPS) in Bremen. “In this respect, the present study confirms this practice and can, if necessary, provide additional clarity and lead to efforts in some practices or clinics.”
The expert is not surprised by the new data; it supports many previous studies. However, the new study also has weaknesses. For example, other factors influencing the cancer risk were not taken into account in all subgroups examined. But this is normal for an international study of this type; the necessary information is simply not available everywhere.