Study links pediatric CT scans to higher cancer risk, urging cautious use of radiation

A government-funded study finds that radiation from commonly used medical imaging tests may triple the risk of cancer in children. The findings come as imaging tests such as CT scans—widely used to diagnose injuries, monitor chronic diseases, and detect cancer—expose patients to ionizing radiation. While these tests can be lifesaving, repeated scans can accumulate small amounts of radiation in the body, a known carcinogen. About 18 percent of Americans—roughly 61 million people—undergo imaging tests like CT scans each year, according to the study's framing of national practice patterns.

The study followed 3.7 million children born between 1996 and 2016 across six U.S. health systems and Ontario, Canada, and tracked them from birth to 2017. It found that radiation exposure from medical imaging was associated with an increase in hematologic cancers, including leukemia and lymphoma, and suggested that cutting unnecessary imaging and lowering radiation doses could prevent a meaningful share of cases. The researchers report that about one in 10 blood cancers among children and teens could be attributed to imaging-related radiation exposure. In particular, exposure from head CT scans was linked to a substantial portion of these cancers.

For children who underwent a head CT, the study estimated that about 25 percent of their cancers could be attributed to radiation exposure. A single or two head CTs were associated with an approximately 1.8-fold increase in the risk of blood cancer, and receiving multiple scans raised the risk to about 3.5 times higher than those who had no scans. Overall, the researchers wrote, medical imaging was associated with about 10.1 percent of hematologic cancers in the cohort. The risk is attributed to unregulated radiation exposure that varies from machine to machine. CT scans can be life-saving when they reveal disease or injury, but experts say they are sometimes overprescribed or performed unnecessarily, potentially due to cost pressures on hospitals or fear of missing a diagnosis and being sued.

Dr. Rebecca Smith-Bindman, the study’s lead author and a radiologist at the University of California, San Francisco, said, “Children are particularly vulnerable to radiation-induced cancer due to their heightened radiosensitivity and longer life expectancy. While medical imaging can be lifesaving, our findings underscore the critical need to carefully evaluate and minimize radiation exposure during pediatric imaging to safeguard children’s long-term health.” She added that imaging should be performed only when it provides essential information and that whenever CT scans are used, they should be conducted with the lowest possible radiation dose.

Dr. Diana Miglioretti, a co-author and professor at UC Davis Health, said the study provides robust, direct evidence of a dose-response relationship between medical imaging radiation and hematologic malignancy risk in children and adolescents. “Our findings align with international research highlighting that children are especially radiosensitive,” she said. “It’s crucial for clinicians to weigh the immediate benefits of imaging against potential long-term health risks and to optimize imaging protocols to minimize radiation exposure.” The research was funded by the National Cancer Institute and grants from the Ontario Ministry of Health and Long-Term Care.

The study’s authors note that a substantial portion of pediatric cancers—roughly 15,000 cases annually in the United States, with leukemia accounting for about 30 percent of child cancer diagnoses—still emerge outside the imaging context. About 1,600 American children die of cancer each year. They also point to a broader trend: childhood cancers have risen by roughly 35 percent over the last half-century, a pattern some researchers link to improved detection as well as environmental factors such as radiation and pollution.

The article emphasizes that, despite the risks, CT scans remain an essential tool in modern medicine for diagnosing bleeding, injuries, and cancers, as well as guiding treatments and surgical planning. The authors urge clinicians to reserve radiation-based imaging for cases where it genuinely changes management and to substitute MRI or ultrasound when feasible. In this cohort, the estimate that medical imaging contributed to about one-tenth of blood cancers underscores the potential impact of careful imaging practices on pediatric health.