Repeated exposure to unnecessary computed tomography (CT) scans may pose a significant cancer risk, a recent study published in JAMA Internal Medicine has found. The research estimates that CT scans performed in the United States in 2023 could lead to approximately 103,000 future cancer diagnoses, accounting for nearly 5% of all new cancer cases in the country.

The study, led by Dr Rebecca Smith-Bindman, a radiologist and professor at the University of California, San Francisco, examined data from 93 million CT scans performed on 62 million patients in 2023. It is expected that CT scans, which involve ionizing radiation, a recognized carcinogen, will result in cancers such as lung, colon, leukemia, and breast cancer in exposed patients over their lifetime.

The study suggests that the risk is particularly more for children and adolescents, though adults, who undergo the majority of scans, account for 91% of the projected cancers. “CT can save lives, but its potential harms are often overlooked,” said Smith-Bindman, a lead researcher on the study. “Given the large volume of CT use in the United States, many cancers could occur in the future if current practices don’t change,” she added.

How does radiation from CT scans cause cancer?

Ionizing radiation from CT scans can damage DNA, increasing the risk of mutations that may lead to cancer. The study found that abdomen and pelvis scans in adults contribute the most to future cancer cases (37%), followed by chest scans (21%). In children, head CTs pose the greatest risk, especially for infants under one year, who are ten times more likely to develop cancer from radiation exposure than adults.  

According to the study, adult abdominal and pelvic scans are the most important in predicting future cancer incidence (37%), followed by chest scans (21%). Head CTs represent the greatest risk to children, particularly newborns under one year old, who are 10 times more likely to get cancer as a result of radiation exposure than adults.

While the risk of a single scan is minor (around a 0.1% increase in lifetime cancer risk), the cumulative effect of repeated scans can greatly raise the risk. With CT usage in the United States increasing by 30% since 2009, the report warns that unregulated activities may pose a public health risk.

Should you avoid CT scans?

Experts say that CT scans still remain essential for diagnosing conditions like cancer, strokes, and internal injuries. However, the study highlights the need to curb unnecessary scans and optimize radiation doses. Alternatives like MRI or ultrasound, which do not use ionizing radiation, could be considered when appropriate.

Stricter protocols

As CT usage continues to increase, the study underscores the need for a balanced approach to medical imaging. The researchers advocate for stricter justification of CT scans, particularly low-value scans that offer minimal clinical benefit. “Reducing the number of scans and reducing doses per scan would save lives,” Smith-Bindman said. 

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