CT scans are essential to modern medicine, quickly diagnosing conditions from strokes to cancer. However, new research suggests that the very tool used to save lives could, in some cases, contribute to future cancer cases.
A University of California–San Francisco study estimates that CT scans performed in 2023 could lead to more than 100,000 future cancer cases—about 5 percent of annual U.S. diagnoses. That level of risk is comparable with other known factors such as alcohol and obesity.
Published in JAMA Internal Medicine, the study concludes that while CT scans remain essential, they should be used more cautiously, especially for children and patients who undergo repeated imaging.
“CT can save lives, but its potential harms are often overlooked,” Dr. Rebecca Smith-Bindman, lead author of the study and UC–San Francisco radiologist, said in a statement. “Reducing the number of scans and reducing doses per scan would save lives.”
Some experts worry that the message lacks balance and may scare patients from necessary care by emphasizing long-term cancer risks without proper context.
“It is frightening to see these numbers,” Dr. Donald Frush, pediatric radiologist at Duke University, told The Epoch Times. “But without putting them in the context of how valuable CT can be, we risk eroding public trust in a tool that saves lives every day.”
Study Scans Deeper
To estimate long-term cancer risk from CT scans, UC–San Francisco researchers analyzed a national sample of 121,212 real-world exams drawn from 143 hospitals in 20 states. The data included detailed information on scan type, radiation dose, and patient demographics.
While children face the highest risk per scan, adults account for most projected cases because of the sheer volume of imaging they receive. Abdominal and pelvic scans were the largest contributors, followed by chest, spine, and head imaging. Among children, those younger than age 1 faced the greatest individual risk—up to 20 cancers per 1,000 scans. Among adults, those aged 50 to 69 are expected to carry the largest share of future CT-related cancers.
Researchers excluded scans from patients’ final year of life, when long-term cancer risk is less clinically relevant. They also ran multiple “what-if” scenarios, with the lowest estimate at 80,000 cancers and the highest at 127,000.
According to study author Diana L. Miglioretti, the increase reflects rising CT use and more precise data on radiation exposure.
“Our projections are higher than previously reported because CT utilization has increased by 30 percent since the earlier study,” she told The Epoch Times via email.
However, some experts believe that the projections may overstate the risk. Cynthia McCollough, radiologist and medical physicist at the Mayo Clinic, questioned whether excluding only the final year of life goes far enough.
“A large portion of CT scans are performed on patients who are in the medical system for diagnosis and treatment of significant disease or injury,” she said in an email to The Epoch Times. “Including these patients in the statistical estimation of possible future cancers is flawed.”
She cited a 10-year follow-up study of patients who had undergone multiple CT exams, noting that half had died within two years, often because of the condition prompting the scan.
While the UC–San Francisco study did exclude scans from the final year of life, McCollough argued that a broader time frame would have been more appropriate, given that most radiation-related cancers take 10 to 40 years to develop.
“Following this approach would greatly decrease the number of CT-related cancers predicted by this study,” she said.
The study authors acknowledged limitations in their approach. The cancer risk models were based on data from Japanese atomic bomb survivors, which may not fully reflect the health profiles or exposures of U.S. patients. They also noted that applying average life expectancies could lead to overstating risks, since many patients who undergo CT scans are already seriously ill and less likely to develop long-term radiation-related cancers.
Smith-Bindman is a co-founder of Alara Imaging, a company that offers free software to hospitals for tracking CT radiation doses. The study notes that Alara Imaging did not participate in the research.
Understanding the Dose
Most people don’t think twice about the radiation in a CT scan. It’s fast, routine, and often feels like just another step toward answers. However, behind the speed is ionizing radiation—which, in large or repeated doses, can increase long-term cancer risk.
Radiation is a medical paradox, integrative physician Dr. Nathan Goodyear said. It can detect and treat cancer—but also, in some cases, cause it.
For most adults, a single CT scan poses low risk—about a one in 2,000 chance of developing cancer, Dr. Max Wintermark of MD Anderson Cancer Center said. For young children, it’s closer to one in 1,000 because of more vulnerable tissue and longer life expectancy.
“The radiation dose from a single CT scan is low—similar to the natural background radiation one might experience over a few years,” Wintermark said in an email to The Epoch Times. “Modern scanners have brought those doses down significantly.”
But radiation risk isn’t just about how much—it’s about what it does.
“X-rays used in CT scans cause DNA breaks,” Madan Rehani, professor of radiology at Harvard Medical School, told The Epoch Times in an email. “Those breaks that do not get repaired or are misrepaired have the potential to lead to cancer many years after they have occurred.”
CT scan radiation can increase cancer risk by damaging DNA, causing mutations, and disrupting cell growth, Miglioretti said. It can also affect nearby cells and trigger oxidative stress, further promoting cancer over time.
While one scan may be fine, many people don’t stop at one. Repeat imaging can cause radiation exposure to add up quickly. The risk then shifts from hypothetical to more substantial, especially if older machines or outdated protocols are used, which often deliver higher doses than modern, optimized systems.
A Tool That Both Helps and Harms
The UC–San Francisco study has renewed concern over radiation exposure, but many experts stress the need to weigh those risks against CT scans’ life-saving benefits.
“Never refer to how many cancer cases CT is responsible for without referring to how many cancer (and other) cases CT is helping to reduce or cure,” Marc Kachelriess, professor at the German Cancer Research Center, told The Epoch Times via email. “Never risks without benefits! Never cons without pros!”
Others take issue with the study’s comparisons. Some experts argue that likening CT scans to well-established lifestyle risks may mislead the public. McCollough called the comparison to alcohol and obesity inappropriate.
