Routine use of CT imaging may contribute to as many as 5% of all cancer cases in the U.S. each year, according to new research published April 14 in JAMA Internal Medicine.

The study, led by researchers at the University of California, San Francisco, attributes this risk to the ionizing radiation used in CT exams and calls for more judicious use of the technology.

An estimated 93 million CT scans were performed in 2023, with researchers projecting approximately 103,000 cancer cases as a result — three to four times higher than earlier estimates. The risk is highest for infants, but adults, who receive the most scans, account for the largest share of projected cases.
“CT can save lives, but its potential harms are often overlooked,” said first author Dr. Rebecca Smith-Bindman, a UCSF radiologist and professor of epidemiology and biostatistics. “Given the large volume of CT use in the United States, many cancers could occur in the future if current practices don’t change.”

In response to the findings, the ACR stressed that concerns about cancer risks from CT scans remain largely theoretical and unsupported by studies based on real-world patient outcomes. No published research has directly linked CT imaging — even when performed multiple times — to cancer.

The ACR recommends that patients keep a record of imaging procedures and ask providers questions before undergoing any scan that involves radiation. “Americans should not forgo necessary, lifesaving medical imaging and continue to discuss the benefits and risks of these exams with their healthcare providers,” the group stated.

The analysis, funded by the National Institutes of Health, examined data from 61.5 million patients. The greatest number of projected cancers was among adults aged 50 to 59, with abdominal and pelvic scans posing the highest risk. In children, head CTs accounted for the majority of predicted cases, with thyroid, lung and breast cancers most common. Infants exposed to CT imaging were found to have a tenfold higher risk of developing cancer.

The authors identified certain exams — such as scans for upper respiratory infections or uncomplicated headaches — as frequently unnecessary. They emphasized the potential to reduce harm by using lower doses.

“There is currently unacceptable variation in the doses used for CT, with some patients receiving excessive doses,” Smith-Bindman said.

Dr. Malini Mahendra, a UCSF assistant professor of pediatric critical care and coauthor, underscored the need for better communication with patients and families. “Few patients and their families are counseled about the risk associated with CT examinations,” she said.

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