RODALE NEWS, EMMAUS, PA—CT scans are important diagnostic tools that can detect cancer tumors as small as an eighth of an inch in diameter. But overuse of the machines could actually be hurting us in the form of excess radiation and an increased cancer risk, according to studies in this month's Archives of Internal Medicine journal.
"The articles in this issue make clear that there is far more radiation from medical CT scans than has been recognized previously, in amounts projected to cause tens of thousands of excess cancers annually," writes Rita F. Redberg, MD, professor of medicine at the University of California–San Francisco. "Also, as these scans have become more sensitive, incidental findings lead to additional testing, and often more radiation, biopsies, and anxiety."
THE DETAILS: To figure out how much radiation medical imaging delivers in order to balance the risk-benefit ratio, researchers looked at 1,119 patients undergoing 11 common types of diagnostic CT scans at four different facilities last year. Researchers looked at hospital records to figure out radiation dosage from each scan and then calculated estimated lifetime risks of cancer that could be attributed to the scans.
The researchers found that radiation varied among machines and area of the body scanned. For instance, a CT abdomen and pelvis scan used about 15 times the amount of radiation used in a head CT scan. Researchers determined CT scan technology used for coronary angiography, a heart scan, at age 40 would result in one in 270 women and one in 600 men developing cancer down the line as a result of the scan. For a lower-radiation-dose CT head scan, an estimated one in 8,100 women and one in 11,080 men who received the scan at age 40 would develop cancer in a lifetime. The risk is doubled for 20-year-old patients, and for 60-year-olds, they are about 50 percent lower.
WHAT IT MEANS: CT scan use has skyrocketed in the last three decades, and the benefits don't come without risk. In 1980, 3 million scans were used. In 2007, that rate jumped to 70 million. And while the percentage of people estimated to get cancer from the scans is low, when you look at how many people are scanned annually, it's clear to see that this could affect many people, particularly if doctors order unnecessary scans, and if patients keep demanding them. "While CT scans can provide great medical benefits, there is concern about potential future cancer risks because they involve much higher radiation doses than conventional diagnostic X-rays," the authors of one report write. (A chest CT scan equals about 100 times the radiation dose of a routine chest X-ray.)
Here's how to balance the benefits of receiving a CT scan against the risks:
• Know when a problem isn't CT scan–worthy. According to Thomas Goetz, author of the upcoming patient-advocacy book The Decision Tree: Taking Control of Your Health in the New Era of Personalized Medicine
• Ask questions. "I'd suggest that when a physician suggests a CT scan, especially if it comes with comments like, 'Just to rule everything out,' that patients stop and ask, 'Do I really need this scan?' That simple gut check can often be enough to avoid impulsive and expensive scans," says Goetz.
• Seek safer alternatives. If you are having a health issue and need medical imaging, ask if an MRI or ultrasound—techniques that don't use radiation—could be used instead.
• Read on. For more information on medical imaging and radiation, check out our story "Is That Scan Really Necessary?"