In 2001, when a paper by P&S researchers found that CT scans pose a small risk of cancer in children, the findings were splashed across newspapers and television programs across the U.S.
And the reaction from many radiologists was scorching.
The study – led by David Brenner, PhD, now the director of Columbia’s Center for Radiological Research – used data collected from Japanese atomic bomb survivors to calculate the cancer risk to a child undergoing a CT scan. Though one to two CT scans expose a child to the same radiation dose experienced by many A-bomb survivors, who have a higher cancer rate than unexposed Japanese, many critics didn’t believe Brenner’s findings were “real.”
David Brenner, with a model used to measure radiation dosage during a CT scan.
Now just over a decade later, a study of children who got CT scans – the first study to look at patients exposed to radiation from CT scans – has confirmed Brenner’s original findings and should help resolve the controversy.
The new study, led by Mark Pearce of Newcastle University and published in The Lancet, identified 178,000 patients in the U.K. who had one or more CT scans before age 22. The researchers then tracked the subsequent cancer history of each individual using the UK National Health Service Registry and found a direct relationship between radiation exposure and cancer.
Based on their calculations, a single CT scan produced approximately one excess case of leukemia and one excess brain tumor for every 10,000 patients in the first decade after the scan.
“That’s quite close to our original risk estimates,” Brenner said. “We calculated one head CT before age 10 would produce 1 excess leukemia and 5 excess brain tumors for every 10,000 patients scanned, over the child’s entire lifetime.
“The message from the Pearce study is that the risks of CT are very small, but real,” he said. “The field can no longer claim that the risks are non-existent or too low to detect.”
The Pearce study should raise more awareness, but pediatric radiology has already changed strikingly since the publication of Brenner’s paper, despite the debate over his findings.
During the past decade, manufacturers of CT machines have designed ways to reduce radiation dose during a scan; The Alliance for Radiation Safety in Pediatrics launched the Image Gently campaign to raise awareness; and pediatric emergency physicians have since developed guidelines to reduce the number of children with minor blunt head trauma who get a CT scan.
“Brenner furnished the explosion required to arouse the profession,” wrote Lee Rogers, MD, the editor in chief of the American Journal of Roentgenology, just a year after the paper was published in his journal.
But Brenner says more progress is needed. CT use has doubled in the last decade and “estimates of the number of scans that are not clinically justified range between 20 percent and 50 percent, depending on the scenario,” he said. “That’s probably the same as a decade ago and far too high.”
P&S cardiologist and radiation researcher Andrew Einstein, MD, PhD, who wrote a commentary published with the Lancet paper, said decreasing the number of unnecessary CTs requires shared responsibility among all healthcare providers.
“Patients should get CT scans when appropriate. Scans are remarkably effective and they save many lives,” he said. “What shouldn’t be done are inappropriate CT scans.
“Reducing that number will require a lot of education for the physicians – understanding radiation doses, the risks, and possible alternative tests – but which will surely be bolstered by the Lancet study.”