Overuse of CT scans could result in 100,000 preventable cancer cases in the USA

CT-associated cancers could eventually account for 5% of all new cancer diagnoses annually in the USA.

A multi-institutional group of researchers from The Institute of Cancer Research (London, UK), Kaiser Permanente (WA, USA) and the University of California (CA, USA) have uncovered that the overuse of CT scans in the USA, could contribute to over 100,000 cases of cancer annually, including nearly 10,000 in children. The findings aid the more careful clinical justification of CT scans and promote dose reduction strategies to prevent avoidable cancers.

CT scans are a vital imaging tool used to diagnose cancer and guide medical treatments. However, when used excessively or without clear clinical justification, they can expose patients to unnecessary ionising radiation, contributing to a significant number of potentially preventable cancer cases.

Since 2009, CT scan usage in the USA has increased by 30%. It has also been noted that radiation doses can vary widely, sometimes being higher than necessary and that scans performed on healthy individuals may offer limited clinical benefit while posing long-term health risks.

To investigate projected lifetime risks from CT imaging, the researchers used a publicly available risk model created by Amy Berrington (co-study lead from The Institute of Cancer Research), which highlights lifetime cancer risk after exposure to radiation and combined this with USA data on the number of CT scans and doses.

Using this risk model, they uncovered that in 2023, approximately 62 million people in the US had 93 million CT scans, which could result in approximately 103,000 future cancers over the course of the lifetime of exposed patients.

The findings suggest that if radiation dose levels and utilization practices continue as they are, CT-associated cancers could eventually account for 5% of all new cancer diagnoses annually in the USA, the same percentage as those caused by alcohol.

“While CT scans are immensely beneficial in diagnosing and detecting many conditions, including cancer, they do involve exposure to ionising radiation that has been shown to increase the risk of developing cancer.”

“It’s important to note that for the individual patient, this increased risk is small, and the benefits far outweigh the risks if the scan is clinically justified. But when millions of CT scans are being carried out across the population, these small risks do add up,” commented Berrington.

The research team hope that their findings will result in either a reduction in the number of low-value CT scans, those which are unlikely to help the patient, or a reduction in the radiation dose per exam.

“CT scans have transformed patient care, and it’s important that people do continue having their scans when they are invited by their doctor. This research will add to the growing body of evidence that indicates that CT scans must only be used when necessary for clinical decision making,” concluded Kristian Helin (The Institute of Cancer Research).