Children Exposed to Radiation From CT Scans Face Increased Blood Cancer Risk

United States performs more CT scans and MRIs per capita than any other developed country, raising concerns about overuse and unnecessary radiation exposure in children.

New research warns computed tomography (CT) scans and other types of medical imaging may cause 10% of all childhood cancers, after finding the risk increases as the dose of radiation increases, a strong indication of a causal connection.

CT scans, also commonly referred to as CAT scans, are a type of medical imaging that uses computers and ionizing radiation to help model internal organs, bones and soft tissue.

The imaging helps to detect and diagnose various medical conditions. However, exposure to the radiation from these scans also increases a patient’s risk of developing new types of cancer. This is especially true for children, who absorb more radiation and have longer life-expectancies.

According to the findings of a study published in The New England Journal of Medicine on September 17, nearly 3,000 childhood cancers were caused by ionizing radiation from CT scans and other medical imaging during a 20-year period.

Prior research, conducted by the same team at the University of California, San Francisco, indicates radiation from CT scans may cause more than 100,000 future cancer cases every year.

Medically unnecessary imaging continues to be a problem in the U.S. compared to other countries. Imaging like CT scans and MRIs are often overused in the United States. In fact, the U.S. has the highest per-capita rate of diagnostic medical imaging than any other developed country.

For the new study, Dr. Rebecca Smith-Bindman and her University of California research team studied data on nearly 4 million children born between 1996 and 2016 in six U.S. healthcare systems and Ontario, Canada. They conducted more than 35 million person-years of follow up and identified more than 2,900 blood cancers that were diagnosed among participants.

According to the findings, of those who developed malignancies, 79% were diagnosed with lymphoid cancers. Another 16% of participants diagnosed with cancer developed myeloid cancers or acute leukemia bone marrow cancers, and 4% developed histiocytic- or dendritic-cell blood cancers.

The data showed the risk of cancer was higher with each increasing dose of radiation a child received. Children exposed to 1 to 5 gray units (Gy) of radiation faced a 41% increased risk of developing cancer. The risk increased to 82% for those who were exposed to 15 to 20 Gy and then to 259% if the child was exposed to 50 to 100 Gy.

A gray is designated as one unit of ionizing radiation, meaning one joule of energy absorbed by one kilogram of matter. It measures how much radiation is physically absorbed by the body during medical imaging.

The average radiation exposure among children who were exposed was 14 to 23 Gy. Researchers said 13.7 Gy is the exposure level from one CT scan of the head and 24.5 to 36.4 Gy was the exposure level among children with blood cancers.

The most common forms of imaging were chest x-rays and CT scans of the head and brain.

Researchers estimate that 10% of all blood cancers diagnosed in the U.S. are linked to exposure to radiation during medical imaging. The highest risks are posed from CT scans, especially as the dose of radiation increases.

Medical imaging like CT scans and x-rays can be lifesaving, but researchers emphasized the findings of the study highlight the need to minimize the level of radiation and the amount of exposure children face. Imaging should only be performed when necessary to diagnose a condition and at the lowest dose possible, researchers warned.