Rise in CT Scans Poses Cancer Risk

Rise in CT Scans Poses Cancer Risk
WEDNESDAY, Nov. 28 (HealthDay News) -- The number of CT scansperformed in the United States has increased dramatically since the 1980s,and that means an increased risk of cancer for patients caused by exposureto high doses of radiation, a new report contends.
Today, more than 62 million CT scans a year are done in the UnitedStates, compared with 3 million in 1980. A CT scan -- an imaging methodthat uses X-rays to create cross-sectional pictures of the body -- canhave radiation doses 50 to 250 times greater than the dose of aconventional X-ray, the report's authors note.
"The radiation doses from CT scans have been clearly demonstrated toincrease cancer risk," David J. Brenner, director of the ColumbiaUniversity Radiological Research Accelerator Facility, said during a newsconference Tuesday. "On an individual basis, not a big individual risk,but a small risk applied to an increasingly large population spellstrouble down the road," he added.
Brenner and his colleague Eric J. Hall, director of the Center forRadiological Research at Columbia University College of Physicians andSurgeons, detailed their concerns in a report in the Nov. 29 issue of theNew England Journal of Medicine.
Cancers from radiation, except leukemia, take years to develop, Brennersaid. "However, in a few decades, 1.5 to 2 percent of all cancers in theUnited States may be due to the radiation from CT scans being done now,"he said.
It takes 20 to 50 years after exposure to radiation before the fulllegacy of that exposure becomes evident, Hall said. "It takes a long timebefore the solid cancers emerge," he said. "The leukemias may come up inthe first decade, but the solid cancers take a long time."
Some 4 million to 5 million CT scans are done on children, and childrenare more sensitive to radiation than adults, Hall added. "A CT scan of theabdomen in a child gives a risk of about one in a 1,000 of an inducedcancer," he said.
One-third of all CT scans, about 20 million a year, are medicallyunnecessary, Brenner said. "Anyone presenting to an emergency room with abelly ache or chronic headache will automatically get a CT scan," he said."Is this justified? Well maybe not."
Brenner said many CT scans could be replaced by other tests that don'tinvolve X-rays, with ultrasound being one example.
"We were astonished to find how many doctors, particularly emergencyroom physicians, really have no idea of the magnitude of the doses or thepotential risks that are involved in CT scans," Hall said.
Brenner said the use of CT scans is growing. New uses includediagnosing lung cancer, virtual colonoscopy and whole-body scans. "Most ofthese have not been proven to have a benefit over the risk," Hallsaid.
Brenner and Hall said they aren't saying that people should avoid CTscans when they are appropriate. "Clearly in a patient that's symptomatic,a CT is a wonderful diagnostic tool," Hall said. "What we are pushing foris to limit the use of CT to situations where it really is needed."
"There are several experiences in the past where radiation was used andwe thought it was fine at the time, and then down the road the legacy ofthese treatments becomes apparent," Hall said. "So we are very concernedabout the built-up public health risk over a long period of time."
Brenner and Hall suggested three ways to diminish the risk from CTscans. First, the radiation dose should be reduced and tailored toindividual patients. Second, CT scans should not be used when otheroptions that have no radiation risk, such as ultrasound or magneticresonance imaging (MRI), are appropriate. And the third suggestion --reducing the number of CT scans prescribed.
Adopting these strategies could keep some 20 million adults and morethan 1 million children from unnecessary radiation exposure each year, theresearchers said.
G. Donald Frey, a professor of radiology at the Medical University ofSouth Carolina, said he agreed that too many unnecessary CT scans areprobably being performed. But, for those who need such a scan, the benefitoutweighs the risk, he said.
"We are concerned that many CTs are done inappropriately," Frey said."The whole community should work together to reduce inappropriate scans,but it would be absolutely tragic if a patient who needed a CT failed toget one because of concerns of the radiation dose."
Also, newer CT scanners have the ability to adjust the dose ofradiation, Frey said.
"When CT scans are done on modern equipment where the dose can beadjusted to individual patient size, and when they are done in facilitiesthat are accredited, the actual doses are being reduced," he said.
Frey noted that there are already guidelines that, if used, couldreduce the number of inappropriate scans.
More information
For more information on CT scans, visit the U.S. National Library of Medicine.