Computed tomography triggers up to 5% of cancers

Scientists from the University of California, San Francisco, have discovered the risk of cancer in patients undergoing CT scans.

It is noted that the CT procedure has become one of the key procedures in the field of health diagnosis. However, patients are exposed to dangerous ionizing radiation, the amounts of which can provoke the onset of cancer.

In a new study, US scientists attempted to determine the level of this risk. They analyzed the results of 93 million CT procedures performed on 62 million Americans in 2023 and estimated that the procedure would result in 103,000 new cases of cancer in the future. To put it another way, this figure represents about 5% of all cancer cases in the U.S. that are detected each year.

Such estimates bring the risks associated with CT on par with those due to alcohol consumption and obesity, which have also been linked to the threat of cancer. The researchers indicated that the most common cancers triggered by undergoing a CT procedure were colorectal cancer and lung cancer. The types of CT scans associated with the most cancers were scans of the abdominal and pelvic regions. According to the study authors, doctors should only use the CT procedure when it is absolutely necessary for a patient.

“CT scans often save lives, but their potential harms are often overlooked, and even very small cancer risks will lead to a significant number of future cancers given the enormous amount of CT scan use in the United States,” the study authors said.

Since 2007, use of the CT procedure in the U.S. has increased by 35 percent. Outside experts have also advocated for some restrictions on the use of the procedure. But they emphasized that there is a great deal of uncertainty in modeling that has tried to estimate absorbed doses to different organs and the increased risk of cancer at specific sites. While some large studies have found a link between CT scans in children and young adults and an increased risk of blood and brain cancers, the risks for adults have largely been extrapolated from studies of those who survived the atomic bombing of Japan or people who were occupationally exposed.

“Because the estimates are based on the best models available to the authors, are indirect, so there is considerable uncertainty about these estimates. So I would say to patients that if you are recommended to have a CT scan, it would be prudent to do so,” said Professor Emeritus of Cancer Monitoring at Queen Mary University of London, Stephen Duffy.

According to him, against the background of the overall risk of cancer incidence, CT scans do not significantly affect the situation. He noted that out of 93 million scans, only 103,000 were associated with cancer incidence, representing only a 0.1% increase in lifetime cancer risk from CT scans. The risk of getting cancer in the US is approximately 40%. Thus, the additional risk from CT scans is small.