A new study finds that CT scans, widely used in U.S. hospitals and clinics, may be linked to nearly 103,000 cancer cases each year.
The findings come from researchers at UC San Francisco and the Institute of Cancer Research in London, who estimate that the radiation from CT scans may now account for up to 5% of all cancer diagnoses in the United States.
The projected impact is especially concerning for younger patients. Researchers estimate that close to 9,700 annual cases could occur in children, with the highest risks found in infants who undergo CT scans before their first birthday.
According to the study, the lifetime cancer risk from CT radiation is ten times higher for babies compared to older patients.
In 2023, about 93 million CT scans were performed across the U.S., a massive increase from just 3 million in 1980. This rapid growth in usage has drawn attention from medical experts who caution that some of these scans are unnecessary and may involve doses much higher than recommended.
Dr. Rebecca Smith-Bindman, a radiologist and professor at UCSF, explained that many patients receive radiation doses two to three times higher than they should. In some cases, the difference in radiation exposure between machines could be as much as 10 to 15 times.
The researchers looked at data from over 93 million CT exams involving 61.5 million Americans. While adults aged 60 to 69 made up the bulk of patients, children still accounted for over four percent of the total. Adults between 50 and 59 were projected to experience the highest number of CT-related cancers, with over 10,000 cases expected in women and more than 9,000 in men.
The most common cancers tied to scan-related radiation exposure include lung, colon, breast, leukemia, and bladder cancers in adults, and thyroid, lung, and breast cancers in children.
The authors noted that the cancer risks are particularly tied to scans of the abdomen, pelvis, and head—areas frequently imaged during routine exams. While they acknowledge that CT scans can be life-saving when medically necessary, they are urging doctors to be cautious and avoid scanning for minor issues like headaches without warning signs or mild respiratory infections.
Although the benefits of CT imaging are widely recognized, especially in detecting serious illness, the study compares the associated cancer risk with other major contributors such as alcohol consumption and obesity. It also draws attention to the lack of consistency in how radiation doses are administered. In response, new rules from the Centers for Medicare and Medicaid Services took effect in January, requiring tighter scrutiny of scan doses across clinics.
Experts involved in the research argue that more transparency is needed. Many patients are never informed of the cancer risks tied to CT imaging, particularly in pediatric cases.
Dr. Malini Mahendra, a pediatric critical care specialist at UCSF, said she hopes the findings will lead to better conversations between doctors and families before a scan is performed.
While individual risk from a single CT scan may be small, the sheer number of scans being performed means the public health consequences could be far-reaching. Researchers are calling on medical providers to adopt lower-dose imaging whenever possible and reduce reliance on scanning when it offers little diagnostic value.