CT Scans Could Be Responsible for 100,000 Cancer Diagnoses Per Year, Study Finds

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New research suggests a common form of medical imaging could be responsible for 5% of all cancer cases annually.

A study conducted by researchers at the University of California (UC) San Francisco suggests radiation from computed tomography scans, better known as CT scans, could lead to lung, breast and other future cancers, with a 10-fold increased risk for babies.

“Given the large volume of CT use in the United States, many cancers could occur in the future if current practices don’t change,” said lead researcher Rebecca Smith-Bindman, M.D., a radiologist and professor of epidemiology and biostatistics and obstetrics, gynecology and reproductive sciences at UC San Francisco, in a news release. “Our estimates put CT on par with other significant risk factors, such as alcohol consumption and excess body weight. Reducing the number of scans and reducing doses per scan would save lives.”

CT scans have become an indispensable tool in modern medicine, offering detailed images of the body’s internal structures. The technology was pioneered by Sir Godfrey Hounsfield in the late 1960s, with the first successful scan performed on a patient in 1971. By 1973, CT scanners were introduced in the U.S., marking the beginning of their widespread clinical use.

Since their inception, the utilization of CT scans has grown exponentially. In 1980, approximately 3 million CT scans were conducted annually in the U.S. By 2021, this number had surged to more than 80 million, according to Harvard Health. This increase reflects the critical role CT imaging plays in diagnosing various medical conditions.

CT scans are commonly employed to assess injuries from accidents, detect tumors, identify infections and evaluate symptoms such as severe headaches or abdominal pain. They are also instrumental in guiding certain medical procedures and monitoring treatment effectiveness. The detailed images provided by CT scans enable health care professionals to make accurate diagnoses and develop effective treatment plans promptly.

However, while CT scans have revolutionized diagnostic approaches for a multitude of conditions and ailments, their use has also been linked to ionizing radiation.

The current study estimated how many future cancer cases in the U.S. could be linked to CT scan radiation in 2023. Researchers used data from the UC San Francisco International CT Dose Registry, which includes millions of real-world CT exams collected between 2018 and 2020.

They analyzed radiation doses by age, sex and scan type, then scaled the data to match the 93 million CT scans performed in the U.S. in 2023.

They projected about 103,000 radiation-related cancers could develop over time from these scans (range, 96,400 to 109,500). While children are more sensitive to radiation, adults made up 95.8% of scans and accounted for about 91% of projected cancers (93,000 cases).

The greatest number of cases were tied to abdomen and pelvis scans (37,500 cases; 30 million scans), followed by chest scans (21,500 cases; 20 million scans). The most common cancer types predicted were lung (22,400 cases), colon (8,700), leukemia (7,900), bladder (7,100) and breast cancer in women (5,700).

“Few patients and their families are counseled about the risk associated with CT examinations,” said Malini Mahendra, M.D., an assistant professor of Pediatric Critical Care at UC San Francisco, in the news release. “We hope our study’s findings will help clinicians better quantify and communicate these cancer risks, allowing for more informed conversations when weighing the benefits and risks of CT exams.”