CT scan warning after doctors raise serious concerns about cancer risk

CT scans commonly taken to help doctors detect injury and disease may also come with an alarming risk - they may account for 5 percent of all cancer cases each year, California physicians said this week.

Radiation from imaging could lead to deadly lung, breast and other cancers, doctors at the University of California-San Francisco said. In 2023 alone, between three and four times more cancers were predicted to result from CTs performed than in previous assessments.

The researchers also found infants under the age of one were 10 times as likely to get cancer than others included in their research.

“Given the large volume of CT use in the United States, many cancers could occur in the future if current practices don’t change,” Dr. Rebecca Smith-Bindman, a professor of epidemiology and biostatistics, warned in a statement.

Smith-Bindman was the lead author of the National Institutes of Health-funded research published Monday in the journal JAMA Internal Medicine.

While the number of annual CT scans, or computed tomography scans, has surged by 30 percent in the U.S. since 2007, it has long been known that the noninvasive x-ray procedure carries a higher threat of cancer. Scans expose patients to ionizing radiation that can increase the risk even with a low dose.

Although everyone is exposed to ionizing radiation every day from the natural environment, added exposures can raise the possibility of developing cancer later in life. Furthermore, CT scans usually require more exposure to radiation than common x-rays because they use a series of images, according to health officials.

To understand more about this relationship, the study’s authors estimated the total number of cancers associated with radiation exposure in relation to the numbers and types of CTs performed in 2023.

They looked at 93 million exams from 61.5 million patients in the U.S., with the majority from adults between the ages of 60 and 69 years old. Of those exams, adults between the ages of 50 and 59 had the highest number of projected cancers, including lung, colon, leukemia, bladder, and breast cancer. Notably, CTs are used in lung and colon cancer screening.

The largest number of cancers in adults would come from CTs of the abdomen and pelvis. In children, they came from CTs of the head.

“Our estimates put CT on par with other significant risk factors, such as alcohol consumption and excess body weight,” said Smith-Bindman. “Reducing the number of scans and reducing doses per scan would save lives.”

The authors warned that some CT scans are overused, including those for upper respiratory infections or for headaches without symptoms.

“Most patients will not develop cancer from a CT scan,” Smith-Bindman told KQED. “But if you’re not getting any benefit, then even a small risk is unacceptable.”

“Every test has potential risks,” Dr. Patricia Nguyen, a cardiologist at Stanford who was not involved in the study, told the station. “And patients should ask: Why am I getting this? What will the result change?”