CT scan radiation poses blood cancer risk in young people

Exposure to increasing radiation doses from computed tomography (CT) examinations may put young people at increased risk of blood cancers, as reported in a large study.

There was clear evidence of a dose-response relationship between cumulative radiation dose to the active bone marrow and the risk of all haematological malignancies. The risk increase occurred across all dose categories beginning at ≥10 mGy, with the greatest risk seen at ≥50 mGy doses versus <5 mGy doses (relative risk [RR], 2.66, 95 percent confidence interval [CI], 1.92–3.70). [Nat Med 2023;doi:10.1038/s41591-023-02620-0]

Every 100 mGy of radiation exposure was associated with a 96-percent increase in the risk of blood cancers overall (excess RR [ERR], 1.96, 95 percent CI, 1.10–3.12). Similar risk estimates were obtained for lymphoid malignancies (ERR, 2.01, 95 percent CI, 1.02–3.42), myeloid malignancies (ERR, 2.02, 95 percent CI, 0.47–4.77), and acute leukaemia (ERR, 1.66, 95 percent CI, 0.43–3.74).

“The analyses presented here showed consistent associations between CT radiation dose and risk of haematological malignancies as a whole, and of lymphoid and myeloid malignancies and acute leukaemia, with an ERR per 100 mGy [of] around 2,” the investigators said.

“With an average active bone marrow dose of 8 mGy for a typical examination today (the average dose in the cohort in 2012–2014), this translates to about a 16-percent increased risk (95 percent CI, 8–24 percent) of these rare malignancies per examination. In terms of absolute risk, among 10,000 children who receive such an examination today, we expect about 1.4 cases (95 percent CI, 1–2) due to CT radiation during the 12 years after the examination,” they pointed out.

The study included 948,174 individuals from the EPI-CT cohort who underwent CT examinations before age 22 years across nine European countries. All of them were followed up for a minimum of 2 years after their first CT.

A total of 790 haematological malignancies, including 578 cases of lymphoid malignancies and 203 cases of myeloid malignancies and acute leukaemia, were documented over a mean follow-up was 7.8 years.

“The results of this study, in which much effort has gone into considering and accounting for possible biases that could affect the risk estimates, strengthen the findings from previous low-dose studies of a consistent and robust dose-related increased risk of radiation-induced haematological malignancies,” the investigators said.

They highlighted the need to raise awareness in the medical community and advocated continued strict application of radiological protection measures in medical settings through justification and optimization of radiological procedures, especially in paediatric populations. For the most part, doses should be kept as low as reasonably achievable while maintaining appropriate image quality for accurate diagnosis.

More work is needed to collect doses and technical parameters in a systematic and timely way in order to better estimate the risks associated with radiation exposure from CT in the future, according to the investigators.