CT Scans Could Trigger More Than 100,000 New Cancer Cases

Over 60 million Americans who underwent CT scans last year could face a troubling future consequence – cancer. A comprehensive new study published Monday in JAMA Internal Medicine projects that the 93 million CT examinations performed in 2023 will ultimately cause approximately 103,000 cancer cases over patients’ lifetimes.

If current practices continue, radiation from these medical imaging procedures could eventually account for about 5% of all new cancer diagnoses annually, placing CT scans on par with alcohol consumption as a cancer risk factor.

Dr. Rebecca Smith-Bindman of the University of California San Francisco, who led the research team, analyzed data from over 120,000 actual CT examinations performed at 143 US hospitals and outpatient facilities across 20 states.

“CT is frequently lifesaving, yet its potential harms are often overlooked, and even very small cancer risks will lead to a significant number of future cancers given the tremendous volume of CT use in the United States,” the researchers wrote in their findings.

The study represents a sobering update to a 2009 analysis that estimated 29,000 future cancers from CT scans performed in 2007. The new projection is three to four times higher, reflecting both increased CT utilization and more precise radiation dose modeling.

Children Face Higher Risks

While only 4.2% of CT recipients were children, they face substantially higher cancer risks per examination. The study found cancer risk in girls younger than one year was 20 cancers per 1,000 examinations versus just 2 per 1,000 in teenage girls aged 15-17.

Despite these elevated risks in young patients, the sheer volume of scans in adults means 91% of projected cancers will occur in the adult population. Adults in their 50s face the highest burden, with CT scans in this age group projected to cause approximately 19,700 future cancers.

Thyroid cancer dominates the pediatric risk profile, accounting for over a third of projected childhood cancers from CT exposure, while lung cancer represents the greatest concern for adults.

Not All CT Scans Carry Equal Risk

Among adults, abdomen and pelvis scans pose the greatest cancer risk, responsible for 37,500 projected cases – more than a third of the total. These scans often employ multiple imaging phases that significantly increase radiation exposure.

“Often these examinations could use single-phase scanning, which would lower doses without impacting diagnostic accuracy,” the researchers noted.

Chest CTs follow as the second highest risk category, with 21,500 projected cancers. Head CT examinations, while generally involving lower radiation doses to critical organs, contribute the most cancer cases among children due to their frequency.

Overall, four cancer types represent the majority of projected cases: lung cancer (22,400), colon cancer (8,700), leukemia (7,900), and bladder cancer (7,100). Among women, breast cancer ranks as the second most common radiation-induced cancer.

Finding Balance

The study authors acknowledge the vital medical value of CT imaging but emphasize the need for caution. CT utilization has grown by 35% since 2007, an increase that cannot be explained by population growth alone.

“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.

The findings highlight the ongoing challenge for healthcare providers: balancing the immediate diagnostic benefits of high-quality medical imaging against long-term radiation risks. For patients, the results underscore the importance of discussing with healthcare providers whether a CT scan is truly necessary or if alternative imaging options might be appropriate.

The research team conducted extensive sensitivity analyses, with cancer projections ranging from