Approximately 103,000 future cancers could result from computed tomography examinations performed in the United States in 1 year, potentially accounting for about 5% of all new cancer diagnoses annually if current utilization and radiation dose levels persist, according to a risk model.

 

Researchers analyzed computed tomography (CT) examination data from 143 U.S. hospitals and outpatient facilities associated with 22 health care organizations across 20 states, then scaled findings to national levels based on 2023 utilization data.

 

"Approximately 93 million CT examinations are performed on 62 million patients annually in the United States, and ionizing radiation from CT is a known carcinogen," reported Rebecca Smith-Bindman, MD, of the University of California San Francisco, and colleagues.

 

Estimated date show that 61,510,000 patients underwent 93,000,000 CT examinations in 2023, with 4.2% of scans performed on children and 95.8% on adults. Patients underwent a mean of 1.5 examinations each, varying by age. After accounting for examinations performed in the last year of life (10.6%), which are unlikely to contribute to future cancers given the average latency period for radiation-induced malignancies, the researchers projected 102,700 lifetime cancers.

 

Despite higher per-scan cancer risk in pediatric patients, adults accounted for 93,000 or 91% of projected cancers due to significantly higher utilization rates, according to the research published in JAMA Internal Medicine. 

Among the projected malignancies, the most common cancers were:

In female patients, breast cancer was the second most common projected malignancy (5,700 cases).

When analyzed by examination type, abdomen and pelvis CT scans in adults were associated with the highest cancer burden, accounting for 37,500 of 103,000 (37%) projected cancers despite representing only 32% of all CT examinations. Chest CT followed with 21,500 projected cancers (21%).

The researchers found that cancer risk was highest in the youngest patients, particularly those under 1 year of age, and decreased with age. For example, the cancer risk in girls younger than 1 year was 20 cancers per 1,000 examinations versus 2 per 1,000 in girls aged 15–17 years.

 

The study's strengths include detailed data on CT utilization and associated radiation dose, detailed calculation of risks with uncertainty limits, and sensitivity analyses that provide a range of estimates under varying assumptions. These sensitivity analyses resulted in projected cancer ranges from 80,000 to 127,000 depending on assumptions about organ doses, pediatric scan proportions, and other variables.

 

This projection is 3 to 4 times higher than a similar 2009 assessment that estimated 29,000 future cancers from CT scans performed in 2007, the researchers noted. The increase is attributed to 30% higher utilization rates, improved modeling of multiphase scanning (which occurs in 28.5% of examinations), and more accurate dose reconstruction methods using examination-level data.

 

"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," the researchers concluded.

 

Disclosures can be found in the published study.