Written by Kimiko Dunbar
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This large retrospective cohort study found a dose-response association between radiation and pediatric hematologic cancer risk. An estimated 10.1% of hematologic cancers were attributable to imaging-related radiation.
There is no safe dose
The U.S. performs more CT scans per capita than any other country. This is especially relevant for children who are more susceptible to radiation and have a longer life expectancy. In this large retrospective cohort study of 3.7 million children from the U.S. and Canada, investigators asked whether radiation from medical imaging increases pediatric hematologic cancer risk. Using detailed dose reconstruction and time-varying Cox models, they found a dose-response association, with relative risks rising from 1.41 for 1–<5 mGy, to 3.59 for 50–<100 mGy, and 5.64 for ≥100 mGy. For reference, one to two CT scans of the head is equivalent to 15-30 mGy exposure, which increases risk by a factor of 1.8. An estimated 10.1% of hematologic cancers were attributable to imaging-related sources of radiation. Limitations include potential residual confounding and reliance on administrative dose estimates. Overall, even <50 mGy exposures (common with CT) were associated with a small but significant increase in hematologic cancer risk, underscoring the need for judicious imaging and dose minimization in children.
How does this change my practice?
We are already pretty darn cautious with CT scans in kids. In fact, the majority of pediatric centers have low-dose CT protocols specifically for this reason. Most pediatric CT scans are not ordered lightly. That said, I think we have room to be even more judicious. Could a fast MRI or ultrasound provide the same information? Could we forgo repeat CT scans when the clinical picture is clear?
Source
Medical Imaging and Pediatric and Adolescent Hematologic Cancer Risk. N Engl J Med. 2025 Oct 2;393(13):1269-1278. doi: 10.1056/NEJMoa2502098. Epub 2025 Sep 17. PMID: 40961449; PMCID: PMC12445590.
