Computed tomography has become one of the most widely used diagnostic tools in modern medicine. From emergency rooms to outpatient imaging centers, CT scans are often the fastest way to detect trauma, internal bleeding, cancer, vascular disease, and a wide range of acute and chronic conditions.
But a major new study published in JAMA Internal Medicine suggests that the sheer scale of CT imaging in the United States may carry long term consequences that are rarely discussed with patients or even fully appreciated at the system level.
According to the analysis, CT scans performed in the United States in 2023 alone are projected to result in approximately 103,000 future cancer cases over the lifetimes of exposed patients. If current utilization and radiation dosing practices continue, the authors estimate that CT associated cancers could eventually account for roughly 5 percent of all new cancer diagnoses each year.
Table of Contents
Why This Study Matters Now
CT imaging volumes in the United States continue to rise, exceeding pre pandemic levels. In 2023, an estimated 93 million CT examinations were performed on more than 62 million patients nationwide.
Even when individual cancer risk from a single CT scan is relatively small, the cumulative population level impact becomes significant when imaging is this common.
This study is one of the most comprehensive attempts to quantify that long term impact using modern utilization data, real world radiation dose measurements, and updated cancer risk modeling.
How the Researchers Estimated Cancer Risk
The research team used data from the UCSF International CT Dose Registry, which includes detailed information from more than 140 hospitals and imaging facilities across 20 states. Unlike older studies that relied on standardized protocols or estimated doses, this analysis reconstructed organ specific radiation exposure using actual scan parameters, patient size, and scanner characteristics.
Key elements of the methodology included:
- Examination level CT dose data from more than 120,000 real world scans
- National CT utilization estimates from IMV Medical Information Division
- Age and sex specific modeling using National Cancer Institute risk assessment software
- Adjustments for scans performed near the end of life, which are unlikely to contribute to future cancer risk
The goal was not to predict cancer in specific individuals, but to understand the population level burden associated with current CT imaging practices.
The Core Findings
After excluding scans performed in the last year of life, researchers estimated that CT imaging in 2023 would result in approximately 102,700 projected lifetime cancer cases, with a plausible range of 80,000 to 127,000 based on sensitivity analyses.
Key findings include:
- Adults accounted for about 91 percent of projected cancers, largely due to higher imaging volume
- Children faced higher cancer risk per scan, particularly at younger ages
- The most commonly projected cancers were:
- Lung cancer
- Colon cancer
- Leukemia
- Bladder cancer
- Breast cancer in women
Although childhood CT exposure has received substantial attention in prior research, this study highlights that adult imaging is responsible for the majority of projected radiation induced cancers simply because adults undergo far more CT examinations.
CT Scan Types Associated With the Highest Risk
Not all CT scans carry equal risk. The study identified specific imaging categories that contribute disproportionately to projected cancer incidence.
Abdomen and pelvis CT scans were the single largest contributor, accounting for approximately 37 percent of projected cancers, despite representing about one third of all CT exams. These scans often involve higher radiation doses and may include multiple imaging phases.
Chest CT scans accounted for roughly 21 percent of projected cancers, reflecting both their frequency and sensitivity of lung tissue to radiation.
In children, head CT scans contributed the majority of projected cancers, largely due to higher radiation exposure to developing tissues and organs.
Multiphase CT imaging emerged as a key driver of higher dose exposure. The authors note that in many cases, multiphase scans could be replaced with single phase imaging without reducing diagnostic accuracy.
Age and Sex Differences in Risk
Cancer risk from radiation exposure is strongly influenced by age at the time of exposure.
The study found that:
- Infants and very young children had the highest cancer risk per CT scan
- Risk decreased steadily with increasing age
- Despite this, adults aged 50 to 69 accounted for the highest absolute number of projected cancers due to frequent imaging
Sex based differences were also observed. Female patients had higher projected rates of certain cancers, including lung and thyroid cancer, reflecting differences in radiation sensitivity included in established risk models.
Putting the Numbers in Perspective
To place the findings in context, the authors compared CT associated cancer risk to other known cancer risk factors.
If annual cancer diagnoses in the United States remain near current levels, CT imaging could eventually account for a similar proportion of cancers as:
- Alcohol consumption
- Excess body weight
- Other established modifiable risk factors
This comparison does not imply that CT imaging is unnecessary or unsafe. Rather, it underscores the importance of appropriate use and dose optimization in a healthcare system where imaging is increasingly common.
Why This Estimate Is Higher Than Past Reports
A widely cited 2009 analysis estimated approximately 29,000 future cancers from CT imaging in 2007. The new estimate is three to four times higher, for several reasons:
- CT utilization has increased by more than 30 percent since 2007
- Multiphase imaging is now more common and was not fully modeled previously
- Organ dose estimation methods are more accurate and individualized
- More granular categorization of CT exam types was used
The authors emphasize that the higher estimate reflects better data and more realistic modeling, not necessarily a sudden increase in danger from CT technology itself.
What This Means for Clinical Practice
CT imaging saves lives every day. It plays a critical role in trauma care, cancer diagnosis, stroke evaluation, and countless other clinical scenarios.
The study’s authors stress that their findings should not discourage appropriate imaging, but rather reinforce core principles of medical imaging safety:
- Imaging should be clinically justified
- Radiation dose should be as low as reasonably achievable
- Multiphase exams should be used only when clearly necessary
- Alternative imaging modalities without ionizing radiation should be considered when appropriate
From a population health perspective, even modest reductions in unnecessary CT use or radiation dose could prevent thousands of future cancer cases over time.
The Broader Public Health Implication
As CT imaging continues to expand across emergency care, outpatient medicine, and preventive screening, the cumulative effects of radiation exposure become increasingly important.
This study suggests that CT imaging is no longer a marginal contributor to population cancer risk, but a meaningful factor that deserves careful attention from clinicians, health systems, and policymakers alike.
Final Takeaway
The projected cancer risk associated with CT imaging is not a reason to avoid medically necessary scans. It is, however, a compelling reminder that imaging decisions matter at scale.
With more than 90 million CT scans performed annually in the United States, thoughtful use, protocol optimization, and ongoing evaluation of imaging necessity could have a substantial long term impact on public health.
Source
Smith-Bindman R, Chu PW, Azman Firdaus H, et al.
Projected Lifetime Cancer Risks From Current Computed Tomography Imaging
JAMA Internal Medicine. Published online April 14, 2025.
https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2832778
