CT Scans in a Single Year Could Result in 100,000 Future Cancers in the U.S.

 

• A risk model suggested that CT exams in 2023 were projected to lead to over 100,000 future cancers over the lifetime of exposed patients.
• Previous projections published in 2009 had estimated that approximately 29,000 future cancers would result from routine CT exposures.
• If utilization and radiation doses remain unchanged in future decades, CT could be responsible for approximately 5% of cancers diagnosed annually.

At current utilization and radiation dose levels, CT exams in 2023 were projected to lead to over 100,000 future cancers over the lifetime of exposed patients, according to an updated risk model.

Among an estimated 62 million patients who underwent 93 million CT examinations in 2023, approximately 103,000 radiation-induced cancers (90% uncertainty limits 96,400-109,500) were projected to result from these examinations, reported Rebecca Smith-Bindman, MD, of the University of California San Francisco, and colleagues in JAMA Internal Medicine.

Risks were higher in children and adolescents, but higher CT utilization in adults accounted for most (91%) radiation-induced cancers.

Previous projections published in 2009 had estimatedopens in a new tab or window that approximately 29,000 future cancers would result from routine CT exposures in the U.S.

"Despite public attention to the potential adverse effects, CT use has grown significantly since 2009," Smith-Bindman and team wrote. "If the number of new cancer diagnoses in the United States remains stable (1.95 million in 2023) and both the utilization and radiation doses from CT remain unchanged in future decades, CT could be responsible for approximately 5% of cancers diagnosed each year. This would place CT on par with other significant risk factors, such as alcohol consumption (5.4%) and excess body weight (7.6%)."

They noted that for the previous projections, the researchers used the best-available data on the volume and distribution of CT examinations, approximations of radiation doses, and associated absorbed organ doses. "Since then, the number of CT examinations performed annually in the United States has increased by more than 30%, more granular data have become available describing examination types, and more accurate methods have been developed for estimating organ dose," they pointed out.

In an accompanying Editor's Noteopens in a new tab or window, Ilana B. Richman, MD, MHS, of the Yale School of Medicine in New Haven, Connecticut, and Mitchell H. Katz, MD, of NYC Health + Hospitals in New York City, noted that while CT is "inextricably woven into the fabric of modern medicine," there are several ways to reduce the reliance on CT, including incorporating diagnostic algorithms at the point of care in order to reduce CT use among low-risk patients, offering alternative imaging solutions like MRI and ultrasound that don't use ionizing radiation, reducing radiation dose, and reducing variations in technique and dose across imaging centers.

"Lastly, educating clinicians about avoiding low-value testing and, in circumstances where alternatives are readily available, involving patients in the decision to do a CT scan may help shift culture and practice," they wrote.

The American College of Radiology (ACR) issued a statementopens in a new tab or window saying that the "theoretical radiation risk" reported in the study is consistent with prior modeling studies "that are not based on actual patient outcomes."

"There are no published studies directly linking CT scans (even multiple CT scans) to cancer," the ACR noted. "Americans should not forgo necessary, life-saving medical imaging and continue to discuss the benefits and risks of these exams with their healthcare providers."

For this study, Smith-Bindman and colleagues developed a risk model using a multicenter sample of CT examinations conducted between January 2018 and December 2020 from the University of California San Francisco International CT Dose Registry.

Lifetime radiation-induced cancer incidence was estimated by age, sex, and CT category using National Cancer Institute software based on the National Research Council's Biological Effects of Ionizing Radiation (BEIR) VII models and projected to the U.S. population using scaled examination counts.

Of the 61,510,000 patients who underwent 93 million CT examinations in 2023, 95.8% were adults, and 53% were female.

The most common cancers were lung cancer (22,400 cases), colon cancer (8,700 cases), leukemia (7,900 cases), and bladder cancer (7,100 cases) overall, while in female patients, breast cancer was second most common (5,700 cases).

Abdomen and pelvis CT exams were estimated to contribute the largest number of projected cancers (40%) in adults (37,500 cases), while head CT exams accounted for the largest number of cancers (53%) in children (5,100 cases).

Sensitivity analyses that reduced and increased organ doses by 20% reflected 22.2% fewer cancers to as many as 23.3% more cancers than the primary analysis.

Smith-Bindman and colleagues acknowledged that the study had several limitations, including the fact that the BEIR VII risk estimated model parameters were based on Japanese survivor outcomes "and questions remain about the transfer of radiation risks from the mid-20th century Japanese population to the current U.S. population."

Disclosures

This research was supported by awards from the National Cancer Institute, the Patient-Centered Outcomes Research Institute, and by residual class settlement funds in the matter of April Krueger v. Wyeth Inc.

Smith-Bindman is a cofounder of Alara Imaging, a company focused on improving the clinical and operational aspects of health systems, including collecting and reporting radiation dose and image quality associated with CT as part of payer-led quality programs.

A co-author reported receiving grants from the NIH.

Richman reported salary support from the Centers for Medicare & Medicaid Services to develop healthcare quality measures. Katz reported no disclosures.

Primary Source

JAMA Internal Medicine

Source Reference: opens in a new tab or windowSmith-Bindman R, et al "Projected lifetime cancer risks from current computed tomography imaging" JAMA Intern Med 2025; DOI: 10.1001/jamainternmed.2025.0505.

Secondary Source

JAMA Internal Medicine

Source Reference: opens in a new tab or windowRichman IB, Katz MH "Balancing computed tomography's benefits with radiation risks" JAMA Intern Med 2025; DOI: 10.1001/jamainternmed.2025.0514.

https://www.medpagetoday.com/hematologyoncology/othercancers/115112