Are we “silently irradiating ourselves to death” in medical imaging?
Science and the Media:
A week after the New York Times op-ed “We are giving ourselves cancer” was published, six letters followed, two of them online only. I asked three physicians, each with decades of experience, about those materials. All three found them important. “Every bit ... needs careful consideration,” one doctor replied. “I thought that whoever selected the responses did a very good job of representing different valid points of view.”
(A fourth longtime physician friend affirmed the discussion’s importance only obliquely, with this quip: “I once saw a patient who was 80 but looked about 50. I asked him, ‘What's your secret?’ He replied, ‘I stay away from doctors.’”)
The op-ed’s coauthors, Rita Redberg and Rebecca Smith-Bindman—a cardiologist and a radiologist, respectively, at the University of California, San Francisco Medical Center—warn that
* “Medical imaging with high-dose radiation—CT scans in particular—has soared in the last 20 years.”
* “Doses of CT scans (a series of X-ray images from multiple angles) are 100 to 1,000 times higher than conventional X-rays.”
* “There is distressingly little evidence of better health outcomes associated with the current high rate of scans.”
* “A single CT scan exposes a patient to the amount of radiation that epidemiologic evidence shows can be cancer-causing.”
* “CTs, once rare, are now routine,” with 10% of Americans annually undergoing one or more.
The two online-only letters say, in effect, that that’s not all. Leana Wen, an emergency physician at the George Washington University and coauthor of When Doctors Don’t Listen: How to Avoid Misdiagnoses and Unnecessary Tests, notes that imaging’s risks also include “severe allergic reaction and kidney failure” and that “incidental findings” can lead to “further, unnecessary testing.” Wen calls for increased attention to informed consent. The second online-only letter, from a doctor of preventive medicine, adds that it “is well established that X-rays and CT scans can cause inflammatory injury to blood vessels and the heart and increase the risk of heart disease.”
Redberg and Smith-Bindman observe that because CT scanners cost millions, “purchasers are strongly incentivized to use them.” In one letter, an internist points to another cost-based incentive. The “pressures of a medical-legal industry that sets a standard of diagnostic precision that borders on fantasy,” he says, should remind readers to consider as well the perverse but real phenomenon of defensive medicine.
The op-ed’s coauthors calculate that “unless we change our current practices, 3 percent to 5 percent of all future cancers may result from exposure to medical imaging.” Much of the Times’s discussion focuses on how to change medical-radiation practice.
The coauthors advocate the principle of making doses “as low as reasonably achievable” (though the shorthand term ALARA never appears). They caution that because specific guidelines don’t exist, doses vary considerably. They continue:
In recent years, the medical profession has made some progress on these issues. The American College of Radiology and the American College of Cardiology have issued “appropriateness criteria” to help doctors consider the risks and benefits before ordering a test. And the insurance industry has started using radiology benefit managers, who investigate whether an imaging test is necessary before authorizing payment for it. Some studies have shown that the use of medical imaging has begun to slow.
But we still have a long way to go. Fortunately, we can reduce the rate of medical imaging by simply avoiding unnecessary scans and minimizing the radiation from appropriate ones. For example, emergency room physicians routinely order multiple CT scans even before meeting a patient. Such practices, for which there is little or no evidence of benefit, should be eliminated.
In one of the letters, Michael Gerardi, president-elect of the American College of Emergency Physicians, explains his disagreement with what he calls the op-ed’s “assertions about what ‘routinely’ occurs in emergency departments.” He points to on-call specialists and primary-care physicians as the main prescribers, while agreeing that minimization is vital.
Redberg and Smith-Bindman call for “clear standards, published by professional radiology societies or organizations like the Joint Commission” or the Food and Drug Administration. They call for tracking doses and for ensuring adherence to the principle of as low as reasonably achievable. They call for patients to inform themselves and ask questions. “Neither doctors nor patients want to return to the days before CT scans,” they acknowledge at the end. “But we need to find ways to use them without killing people in the process.”
The long first letter to the editor engages that question of what’s to be done. The writer, Paul Ellenbogen, represents the American College of Radiology, which maintains a Dose Index Registry that “allows providers to submit anonymous dose data for each scan performed, compare their doses to regional or national levels, and make adjustments based on real-world data.” He recommends government backing for the registry, calls for “wider adherence to medical society guidelines,” advocates mandatory accreditation of medical-imaging facilities, and plugs pending legislation that would mandate use of “physician-developed appropriateness criteria” embedded in “electronic ordering systems” that would automatically advise prescribers. Ellenbogen proposes that such measures “would significantly reduce unwarranted medical radiation to Americans without interfering in the doctor-patient relationship or affecting access to care.”
In the only letter not yet mentioned, three Massachusetts General Hospital radiologists remind readers that the entire discussion is about tradeoffs. They express agreement about the dangers and the need for precautions, but they warn that “encouraging patients to decline appropriate care can also cause them harm.” They cite a study “of 22,000 adults 18 to 35 undergoing body CT” that “showed that the short-term risk of a patient’s dying from his underlying illness is 4 to 7 percent.” This, they write, “dwarfs his lifetime risk of radiation-induced cancer, estimated at 0.1 percent.”
Steven T. Corneliussen, a media analyst for the American Institute of Physics, monitors three national newspapers, the weeklies Nature and Science, and occasionally other publications. He has published op-eds in the Washington Post and other newspapers, has written for NASA's history program, and is a science writer at a particle-accelerator laboratory.