CT Scan Overuse May Up Cancer Risk

Radiation from the increasingly popular computed tomography scanning machines may be causing cancer, a new study finds, but experts say this shouldn't deter people who need the scans from getting them.

In a new study published in the New England Journal of Medicine, researchers at the Columbia University Medical Center in New York estimate that CT scans could cause as much as 2 percent of all cancers in the United States in the next 20 to 30 years.

Some experts point out that this is just a theoretical estimate based on data from Japanese victims of the atomic bomb. Still, the predictions have many worried about the possible increase in cancer risk that accompanies these tests.

"It has been pretty clearly demonstrated that [radiation] doses in CT scans have increased cancer risk," says study author David Brenner, a professor of radiation oncology at Columbia.

"Although the risks for any one person are not large, the increasing exposure to radiation in the population may be a public health issue in the future."

And while radiologists agree that there are cancer risks associated with CT scans, they say that no controlled epidemiological studies have been done to show how great this risk is.

"There is no definitive evidence to suggest the risk is as bad as they state," says Dr. Carl Schultz, professor of clinical emergency medicine at the University of California Irvine School of Medicine. "I'm not saying radiation is good. I am saying we have absolutely no idea what the real lifetime risk from CTs is."

CT imaging is used today to diagnose a wide array of diseases -- from hemorrhages in the brain to cancer in lungs to appendicitis. During the procedure, X-ray machines rotate around a section of the body, taking cross-sectional pictures that computers assemble into a 3-D image.

Although the image is a big improvement over conventional X-rays, the radiation dose that patients receive is also much higher. Researchers say an abdominal CT scan exposes patients to 50 times more radiation than an X-ray of the same region does.

"The important part of this article is that newer, more powerful imaging tools result in greater radiation exposure," says Robert Smith, director of cancer screening at the American Cancer Society. "In summary, concerns about excess exams and excess exposure, especially among pediatric patients, are appropriate."

Children at Special Risk

The risk is especially high for children. Researchers say that children are 10 times as sensitive to the radiation as adults are, putting them at an even greater cancer risk.

"Children's tissues are more sensitive to radiation, and they live longer than adults do, which means the cancer has more time to develop," says Cynthia McCollough, a radiological physicist at the Mayo Clinic in Rochester, Minn. "However, if you need a CT scan, parents shouldn't lose a minute of sleep over it."

The reason parents shouldn't be too concerned is that the individual risk of developing cancer is small.

"One in four Americans will develop cancer in their lifetime," explains McCollough. "That's 25 percent. Radiation from CT scans when you are a baby increases your risk of developing cancer to 25.1 percent."

Really, What's the Risk?

Although radiology experts agree there is a small risk of cancer, they disagree about exactly how high that risk is.

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