Exposure to CT Radiation and Risk of Blood Cancers in Young Patients

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Investigators may have uncovered an association between exposure to computed tomography (CT) radiation in young patients and an increased risk of hematologic malignancies, according to a recent study published by Bosch de Basea Gomez et al in Nature Medicine. These recent findings highlighted the significance of continuing to apply strict radiologic protection measures in young patients.  


Currently, more than 1 million young patients in Europe undergo CT scans each year. The impact of these scans in patient management—including diagnostic efficacy, treatment planning, and disease follow-up—is generally considered positive. However, the extensive use of this procedure in recent decades has raised concerns in the medical and scientific community about the potential cancer risks associated with exposure to ionizing radiation, particularly in young patients.

“The exposure associated with CT scans is considered low (< 100 mGy), but it is still higher than for other diagnostic procedures,” explained senior study author Elisabeth Cardis, PhD, Head of the Radiation Group at the Barcelona Institute for Global Health.

Previous studies have suggested that young patients exposed to CT scans may have an increased risk of developing cancer, but these studies faced several methodologic limitations.

Study Methods and Results

In the recent multinational EPI-CT study, the investigators—including clinicians, epidemiologists, and dosimetrists from Belgium, Denmark, France, Germany, the Netherlands, Norway, Spain, Sweden, and the United Kingdom—analyzed the data of 984,174 patients who underwent at least one CT scan prior to age 22 to address the limitations of the previous research.

The dose of radiation delivered to the bone marrow was estimated for each of the patients. By linking this information to national cancer registries, the investigators were able to identify those who developed hematologic malignancies after an average follow-up of 7.8 years. However, for those who had CT scans in the early years of the technology, the investigators were able to monitor cancer incidence for more than 20 years after their first scan.

The investigators determined there was a clear correlation between the total radiation doses to the bone marrow from CT scans and the risk of developing both myeloid and lymphoid malignancies. A dose of 100 mGy multiplied the risk of developing a hematologic malginancy by a factor of about three. The investigators suggested that a typical scan today (with an average dose of about 8 mGy) may increase the risk of developing hematologic malignancies by about 16%.

“In terms of absolute risk, this means that, for every 10,000 [young patients] who have a CT scan, we can expect to see about [one to two] cases of cancer in the 12 years following the examination,” emphasized lead study author Magda Bosch de Basea Gomez, MSc, PhD, a researcher at the Barcelona Institute for Global Health.


“Implementing this large, multinational study was challenging; it involved extracting data from radiology records of 276 hospitals and linking them to population-based registries in nine countries, all while maintaining the confidentiality of the [patients’] data,” noted Dr. Cardis.

The investigators revealed that more research may be needed to ensure that radiation doses and technical parameters are systematically and adequately collected in the clinics in real time to further improve risk estimates in the future. Although radiation doses from CT scans have decreased substantially in recent years, the new findings underlined the need to raise awareness among the medical community and to continue to apply strict radiation protection measures—especially in the youngest 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,” Dr. Cardis concluded.

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