Cancers deaths | CT scans | Radiation from CT scans linked to cancers deaths
CT scans deliver far more radiation than has been believed and may contribute to 29,000 new cancers each year, along with 14,500 deaths, suggest two studies in today’s Archives of Internal Medicine. One study, led by the National Cancer Institute’s Amy Berrington de Gonzalez, used existing exposure data to estimate how many cancers might be caused by CT scans.
Another study in the journal suggests the problem may even be worse. In that study, researchers found that people may be exposed to up to four times as much radiation as estimated by earlier studies. While previous studies relied on dummies equipped with sensors, authors of the new paper studied 1,119 patients at four San Francisco-area hospitals, says author Rebecca-Smith Bindman of the University of California-San Francisco. Based on those higher measurements, a patient could get as much radiation from one CT scan as 74 mammograms or 442 chest X-rays, she says.
Young people are at highest risk from excess radiation, partly because they have many years ahead of them in which cancers could develop, Smith-Bindman says. Among 20-year-old women who get one coronary angiogram, a CT scan of the heart, one in 150 will develop cancer related to the procedure.
Not all doctors agree about those risks. Scientists have not yet determined whether low doses of radiation actually increase cancer risk or whether the risk rises only after exposure levels reach a certain threshhold, says James Thrall, chairman of the American College of Radiology.
He says it’s also tricky to compare cancer rates between people who have had CT scans with those who haven’t. People undergoing scans may have underlying health problems that predispose them to cancer, he says.
In many cases, CT scans can be lifesaving. In other cases, there’s no evidence a CT scan is really better than other approaches, Smith-Bindman says. Up to one-third of all CT scans are unnecessary, according to an accompanying editorial by Rita Redberg, also of UCSF.
Doctors sometimes order CT scans for convenience because they don’t have access to results at another facility, says Rosaleen Parsons, chair of diagnostic imaging at Philadelphia’s Fox-Chase Cancer Center, who wasn’t involved in the new studies.
She suggests that patients keep their medical records and ask doctors about alternatives that don’t involve radiation exposure.
Patients also should ask if a facility has been accredited by the American College of Radiology, she says.
Media coverage of the two recent studies published in the Archives of Internal Medicine, claiming increases in cancer due to use of computed tomography (CT), raises vital public policy issues that must be considered.
First, it’s important to understand that medical imaging manufacturers have made incredible strides in innovating advanced equipment that minimizes radiation dose. In fact, new medical imaging technologies and systems introduced during the past 20 years have significantly reduced radiation dose.
Even with this progress, manufactures continuously explore the next frontiers of innovative medical imaging technology that will exponentially reduce radiation exposure while exponentially increasing the capability and quality of the images it delivers — allowing physicians to save more lives. To that end, we believe policymakers should encourage technologic development so that companies can continue to innovate and produce diagnostic equipment that reduces radiation dose and improves patient outcomes.
Next, while nobody disputes the effectiveness of CT scans, the assertion that CT scans are overused is an outdated perception. In fact, an analysis of Medicare claims data from 1998-2007 demonstrates that beginning in 2007, spending on advanced diagnostic equipment decreased by 19.2 percent while volume grew by a modest 1.9 percent. Any claims that the use of CT is rapidly growing is false.
Imaging manufacturers believe that the way to continue driving proper use of CT, as well as other diagnostic equipment, is to ensure physicians have access to, and are relying on, evidenced-based guidelines at the point of care to determine which diagnostic test should be ordered (or not ordered). That’s why MITA strongly endorses a robust build-out of appropriateness criteria in the Medicare program, and research supports this approach. This is the best way to drive proper utilization while ensuring patients have access to the diagnostic procedures they need.
Lastly, it’s important to point out that medical imaging, when used appropriately, minimizes other risks that more invasive procedures present to patients, and enables doctors and patients to more effectively tackle the very real and very deadly diseases they already have. We must preserve access to these scans while smartly fostering the development of new technologies and ensuring their proper use.
Medical Imaging & Technology Alliance (MITA)