Computed tomography (CT) has revolutionised medical diagnostics by enabling rapid and detailed internal imaging. Its widespread use has contributed to improved clinical decision-making and outcomes. However, CT also exposes patients to ionising radiation, which carries a measurable risk of cancer. A recent risk projection study has provided an updated estimate of future cancer burden associated with CT use in the United States. Drawing on comprehensive, real-world data from over 90 million CT examinations performed in 2023, the study projects that current patterns of CT use could lead to more than 100,000 new cancer cases over the lifetime of those exposed. This projection, more than triple earlier estimates, raises critical concerns for public health and imaging practice.
CT Utilisation and Dose Modelling
The study utilised data from the University of California San Francisco's International CT Dose Registry, encompassing over 143 US institutions and over 120,000 patient records. These data were integrated with national imaging volume estimates to model population-wide cancer risks. In 2023, an estimated 93 million CT scans were performed on 61.5 million individuals in the United States. Adults comprised the vast majority of these scans (96.7%), with children accounting for just 3.3%. On average, each patient underwent 1.5 examinations, and utilisation peaked among adults aged 60 to 69 years.
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The analysis categorised CT scans into 26 types based on body region and clinical indication, capturing dose variations driven by acquisition protocols and patient characteristics such as age, sex and body size. Organ-specific radiation doses were estimated using a Monte Carlo simulation and advanced anthropomorphic phantoms tailored to patient morphometry. These were then used to calculate lifetime cancer risks via the National Cancer Institute’s Radiation Risk Assessment Tool, which applies risk coefficients from the BEIR VII report.
Projected Cancer Burden by Age, Sex and CT Category
The study projects approximately 103,000 future cancers in patients undergoing CT in 2023, with a 90% uncertainty range of 96,400 to 109,500 cases. Although children face higher per-examination cancer risks, the bulk of projected cases (91%) stem from adult exposures due to far greater utilisation. Lung cancer is the most frequently projected CT-related cancer, followed by colon cancer, leukaemia and bladder cancer. In women, breast cancer is notably the second most common, while thyroid cancer tops the list for children.
Adults aged 50 to 59 years contribute the most to projected cases, with over 19,000 cancers anticipated in this age bracket alone. CT scans of the abdomen and pelvis, which often involve high-dose multiphase protocols, account for the largest share of cases at 37%. Chest and spine CTs are the next largest contributors. In children, head CT scans—commonly used for trauma or neurological evaluation—account for more than half of projected cancers. This age-specific distribution underscores both the elevated sensitivity of young tissues to radiation and the predominance of adult imaging volumes in shaping overall cancer burden.
Sensitivity Analyses and Public Health Implications
A series of sensitivity analyses tested the robustness of the cancer estimates under alternative assumptions. Adjusting organ doses by ±20% produced a projected range from 80,000 to 127,000 cancers. Altering assumptions about scan volume and risk coefficients for female lung cancer yielded similar magnitude changes. These findings affirm that even conservative modelling predicts tens of thousands of radiation-induced cancers tied to current CT practices.
This projected burden translates to approximately 5% of annual US cancer diagnoses if CT utilisation and dosing patterns persist. The risk is on par with major lifestyle-related factors such as alcohol use and overweight status. Compared to a 2009 study that estimated 29,000 future cancers from CT use, the new figures reflect improved dosimetry, more detailed scan categorisation and the sharp rise in scan numbers, up by over 30% since 2007. Additionally, factors such as increased use of multiphase imaging and underrecognised low-value scanning have contributed to the growth in projected risk.
CT imaging remains a cornerstone of modern medicine, often providing critical, life-saving insights. Yet its associated risks, particularly those involving ionising radiation, must be more carefully managed. The latest projections suggest that if current practices continue, CT scans performed in a single year could lead to over 100,000 future cancer cases. This finding reinforces the urgent need for stricter adherence to justification and dose optimisation principles in imaging. Reducing unnecessary examinations and minimising radiation exposure through improved protocols are essential strategies to mitigate this substantial and preventable public health risk.
Source: JAMA Internal Medicine
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