Computer tomography scans, or CT scans, are an invaluable tool for diagnosing cancer and other conditions. But in a cruel twist, the medical imaging technique may be more harmful than once thought, causing alarming rates of the destructive disease as it's overused, a team of researchers from the US and the UK have found.
Their findings, published as a provocative study in the journal JAMA Internal Medicine, indicate that CT scans could cause five percent of all cancers in the US, where 93 million CT scans were performed on 62 million patients in 2023.
In sum, they estimate that about 103,000 future cases of cancer will develop as a result of all the CT scans performed that year — a grim toll that's especially urgent to consider as the number of these examinations performed in the US has risen by 30 percent since 2009, the researchers note.
"The goal is not to scare patients, but to help them understand going forward they need to think about every time a CT is suggested," joint senior author Amy Berrington, leader of the Clinical Cancer Epidemiology Group at the Institute of Cancer Research in London, told San Francisco Chronicle. "Do they need it? Do they understand why it's done and work with their physician?"
CT scans use beams of x-rays that are rotated around your body to provide images with much higher detail than a conventional x-ray. Rather than a flat image, the computer stitches the scans together to form cross-sectional slices, enabling a radiologist to clearly see internal organs and medical issues like tumors.
Naturally, exposing a patient to x-ray radiation comes with some risk. The radiation dose is low, though, and in many cases the upsides of catching the early onset of cancer or some hidden internal bleeding, for example, outweigh the dangers.
But perhaps we ought to be reconsidering that calculus — or at least, not be so CT-trigger-happy. These latest findings indicate a cancer risk three to four times more than previous research, the authors said.
The team analyzed the nearly one hundred million CT scans performed in 2023, throwing them into a risk model that accounted for the type of scan performed, what organs and body parts it targeted, the doses of radiation used in each instance, and the patient's age and sex.
Children were the most vulnerable group. From the 2.5 million scans performed on youths, about 9,700 cancers will develop, the team found. But adults are in plenty of danger, too, since they're more likely to have the scans done — multiple times, even. Patients between the ages of 60 and 69 were the age group with the most scans, accounting for nearly ten million in all.
The most common projected cancers were lung cancer, colon cancer, leukemia, and bladder cancer. As for the most problematic type of CT scan, the largest number of cancers — 37,500 — were projected to arise from abdomen and pelvis imaging, which represented about a third of all CT examinations performed in 2023.
While it's not clear why the use of the imaging technique has risen so dramatically over the past decade or so, the authors caution moderation for both doctors and patients.
"These future cancer risks can be reduced either by reducing the number of CT scans (particularly low value scans which are used in situations where they are unlikely to help the patient) or by reducing the doses per exam," said study lead author Rebecca Smith-Bindman, a radiologist at the University of California San Francisco, said in a statement.
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