Computed tomography imaging performed in the US in 2023 was projected to be associated with approximately 103,000 future radiation-induced cancers, according to a modeling study published in JAMA Internal Medicine that used more granular examination-level radiation dose data than prior national estimates.
The estimate was about three to four times higher than a 2009 projection of future cancers associated with computed tomography (CT) use in the US. The researchers attributed the increase to higher CT utilization, improved organ-dose reconstruction using examination-level data, and the inclusion of multiphase scanning, which was not modeled in the earlier estimate.
Researchers estimated that 93 million CT examinations were performed in 61.5 million patients in 2023, including 3.1 million examinations in 2.6 million pediatric patients and 89.9 million examinations in 58.9 million adult patients. The researchers estimated that CT-associated cancers could eventually account for about 5% of new cancer diagnoses annually in the US if current CT utilization, radiation doses, and baseline cancer incidence remain stable over future decades, although future shifts in imaging patterns or cancer incidence could alter that estimate.
The risk model used examination-level data from the University of California San Francisco International CT Dose Registry, which included CT examinations from 143 hospitals and outpatient facilities across 20 states. National CT utilization estimates were derived from the IMV Medical Information Division CT Market Outlook Report.
The researchers classified examinations by age, sex, and CT category. Pediatric estimates were based on examinations performed from 2018 to 2020, and adult estimates were based on examinations performed in 2020. Examinations performed in the last year of life were excluded from cancer-risk projections because they were considered unlikely to contribute to future radiation-induced cancers.
Organ-specific radiation doses were estimated using Monte Carlo radiation transport simulations based on examination-level technical parameters and patient size. Lifetime cancer risks were projected using the National Cancer Institute Radiation Risk Assessment Tool, which incorporates models based on the National Research Council’s Biological Effects of Ionizing Radiation VII report.
Overall, the researchers projected 102,700 future radiation-induced cancers associated with CT examinations performed in 2023. Adult imaging accounted for most projected cancers, with 93,000 cases, compared with 9,700 cases linked to pediatric imaging. Although risk per examination was highest among younger pediatric patients, especially infants, substantially higher CT use among adults drove most of the projected cancer burden.
The magnitude of pediatric risk varied by age. For example, the projected cancer risk was approximately 20 cancers per 1,000 CT examinations among girls younger than 1 year, compared with 2 cancers per 1,000 examinations among girls aged 15 to 17 years. In a sensitivity analysis using IMV’s higher estimate of pediatric CT utilization, total projected cancers increased to 114,000, and the share attributed to childhood imaging increased from 9% to 23%.
Lung cancer was the most common projected cancer type, with 22,400 cases, followed by colon cancer, leukemia, bladder cancer, and stomach cancer. Among female patients, breast cancer was the second most common projected malignancy.
Abdomen and pelvis CT contributed the largest projected cancer burden overall, with 39,100 projected cancers, including 37,500 among adult patients. Chest CT accounted for 22,700 projected cancers overall, including 21,500 among adult patients. Among pediatric patients, head CT accounted for the largest projected burden, with 5,100 projected cancers.
Multiphase scanning was one of the most clinically actionable contributors to projected risk. The researchers reported that multiphase scanning occurred in 28.5% of examinations and noted that high-dose abdomen and pelvis CT, full-body CT, and spine CT were associated with greater projected risk because of higher radiation exposure. In many cases, the researchers wrote, single-phase scanning could reduce dose without affecting diagnostic accuracy.
Sensitivity analyses produced estimates ranging from approximately 80,000 to 127,000 projected cancers, depending on assumptions about CT volume, organ dose, pediatric utilization, latency modeling, and other factors.
The researchers emphasized that the findings were based on modeled rather than observed cancer outcomes. They also noted that the risk estimates relied largely on models derived from Japanese atomic bomb survivor data, which may not fully reflect repeated low-dose x-ray exposure from CT in contemporary US patients. The model incorporated a dose-and-dose-rate reduction effectiveness factor of 1.5, which assumes low-dose radiation exposure is less harmful per unit than higher-dose exposure. The researchers noted that some evidence supports a lower dose-and-dose-rate reduction effectiveness factor, which would push estimates toward the upper sensitivity range, whereas other evidence supports the value used in the model.
The findings do not suggest that clinically indicated CT should be avoided. Rather, the researchers and accompanying editorialists emphasized reducing low-value imaging, considering ultrasound or magnetic resonance imaging when appropriate, using diagnostic algorithms at the point of care, and standardizing dose protocols across imaging sites.
A correction issued June 2, 2025, addressed errors in Figure 1 and Supplement 1 but did not alter the study’s primary findings or conclusions.
“Justification of use and optimization of dose, including consideration of the need for multiphase examinations, are the tenets of CT imaging and must be applied uncompromisingly to mitigate potential harm,” wrote lead study author Rebecca Smith-Bindman, MD, of the University of California, San Francisco, and colleagues.
Disclosures: The study was funded by the National Cancer Institute, the Patient-Centered Outcomes Research Institute, and residual class settlement funds from litigation involving Wyeth Inc. Dr. Smith-Bindman reported being a cofounder of Alara Imaging Inc, which focuses on collecting and reporting radiation dose and image quality data associated with CT imaging as part of payer-led quality programs. The researchers stated that the work did not overlap with Alara’s commercial activities. Diana L. Miglioretti, PhD, reported receiving grants from the National Institutes of Health during the study. No other disclosures were reported. The funders had no role in the study design, conduct, analysis, manuscript preparation, or publication decision.
Source: JAMA Internal Medicine
