Radiation From CT Scans in Youth Linked to Cancer

Exposure to radiation from CT scans before the age of 22 may increase the risk of blood cancers later in life, a new study suggests.

Computed tomography (CT) is an effective screening tool for tumors, infections, and blood clots. Although the exposure associated with CT scans is less than 100 mGy and qualifies as low, it is still higher than radiation from other diagnostic procedures.

Therefore, the extensive use of CT scans has long raised concerns about the potential cancer risks associated with exposure to ionizing radiation, particularly in young patients. This led to a reduction in the number of pediatric CTs in many countries and a reduction in the pediatric dose.

The new multinational study led by the Barcelona Institute for Global Health and published in Nature Medicine analyzed data from nearly one million people from nine European countries who underwent at least one CT scan before age 22.

Using information from national cancer registries, the researchers identified 790 patients who developed blood cancer during an average follow-up of 7.8 years. Fifty-one of these patients received the diagnoses before the age of 20.

They found a strong link between the total radiation doses delivered to the bone marrow, where blood cells are produced, and the risk of developing both myeloid and lymphoid malignancies. These include forms of blood cancer such as acute myeloid leukemia, Hodgkin’s and non-Hodgkins lymphoma, and myeloma.

A dose of 100 mGy was found to increase the risk of developing blood cancer by about threefold. This suggests that a typical scan today (with an average dose of about 8 mGy) raises the risk of these malignancies by about 16%.

In terms of absolute risk, this means that, for every 10,000 children who have a CT scan, we can expect to see about 1-2 cases of cancer in the 12 years following the examination.

First author Magda Bosch de Basea

The study doesn’t prove a direct cause between a CT scan and blood cancer risk. Nevertheless, the researchers say the findings highlight the importance of continuing to apply strict radiological protection measures, particularly in pediatric patients.

“The procedure must be properly justified – taking into account possible alternatives - and optimized to ensure that doses are kept as low as possible while maintaining good image quality for the diagnosis,” Elisabeth Cardis, Head of the Radiation Group at ISGlobal and senior author of the study.

Dr. Sarah McQuaid, Chair of the Institute of Physics and Engineering in Medicine’s Nuclear Medicine Special Interest Group, says that the study indicates that there could be a small cancer risk from CT scans in young people.

She adds, “But it is important for this to be viewed in the context of the substantial benefit these scans bring, due to the important diagnostic information they provide.”

The symptoms of blood cancer

Blood cancers are caused by DNA mutations, but environmental factors such as exposure to radiation or certain chemicals may also increase the risk of developing the condition.

Epstein-Barr virus, HIV, and human T-cell lymphoma/leukemia virus infections are also considered to be risk factors for developing lymphomas and leukemias.

Symptoms of blood cancers typically include:

• Fever, chills
• Night sweats
• Persistent fatigue, weakness
• Bone and joint pain
• Unexplained weight loss
• Itchy skin or skin rash
• Frequent infections
• Swollen lymph nodes in the neck, underarms or groin
• Anemia

Despite showing a strong association, the study does not prove that exposure to radiation from CT scans in youth causes blood cancers.