A new study from the University of California, San Francisco, has raised serious concerns about the risks of using CT scans too often or with high doses of radiation. According to this research, CT scans may be responsible for about 5% of all cancers in the United States each year.
That’s a big number—around 103,000 cancer cases in 2023 alone—based on the 93 million CT scans performed that year. These figures are much higher than past estimates, which may have missed the full impact of this type of medical imaging.
CT scans, also known as computed tomography, are a common tool in modern medicine. They help doctors look inside the body to find injuries, tumors, or infections. They’re especially useful when quick decisions need to be made, such as during an emergency.
In fact, CTs are used so often now that their use in the U.S. has increased by about 30% since 2007. However, while they are very helpful, they also come with a hidden danger: radiation.
The type of radiation used in CT scans is called ionizing radiation. This kind of radiation can damage DNA in our cells, which may lead to cancer over time. While this risk has been known for years, it hasn’t received as much attention as it should. The new study, published on April 14 in JAMA Internal Medicine, aims to change that.
The lead author, Dr. Rebecca Smith-Bindman, is a radiologist at UCSF who also teaches about public health. She pointed out that CT scans do save lives, but the risks are often not discussed.
According to her, the number of future cancers that may result from current scanning habits puts CT use in the same category as other major cancer risks, like drinking too much alcohol or being overweight.
The study looked at over 93 million CT exams performed in 2023 on more than 61 million people. Unsurprisingly, most scans were done on adults, especially those between 60 and 69 years old.
However, even babies, children, and teenagers got scans—about 4.2% of the total. For this analysis, the researchers left out scans performed during a person’s last year of life, since those wouldn’t be likely to lead to future cancer.
What they found is concerning. Adults aged 50 to 59 were at the highest risk, with over 10,000 new cancers expected in women and over 9,000 in men. The most common types of cancer predicted from CT exposure were lung, colon, bladder, leukemia, and breast cancers in adults. For children, thyroid, lung, and breast cancers were the most likely.
In adults, most future cancers were linked to CT scans of the abdomen and pelvis. In children, the most harmful scans were those of the head. Babies under one year old were at the greatest risk of all. A single scan at that age could increase their risk of cancer tenfold compared to others in the study.
The researchers said that many CT scans are done when they may not be necessary. For example, scans for mild colds or headaches that don’t show signs of something serious may not help but could still cause harm in the long run. They believe that fewer and lower-dose scans could reduce the number of future cancer cases.
Dr. Smith-Bindman also pointed out that there’s a lot of inconsistency in how much radiation is used in CT scans. Some patients are exposed to much higher doses than needed. Lowering the dose doesn’t always affect the quality of the image, but it can reduce the risk of harm.
Another co-author, Dr. Malini Mahendra, who works in pediatric critical care at UCSF, stressed the importance of informing families. She said that many parents don’t realize that CT scans can increase their child’s cancer risk. This study can help doctors explain the risks better so that families can make more informed decisions.
In summary, this study shines a light on a growing concern in modern medicine. CT scans are extremely useful and sometimes lifesaving, but they are being used more often and with higher doses of radiation than necessary. This could lead to thousands of cancers that might be avoided with more careful use.
The researchers urge hospitals, doctors, and patients to work together to reduce unnecessary scans and lower radiation doses. Doing so could save many lives in the years to come.
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The research findings can be found in JAMA Internal Medicine.
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