Study: CT Scans Increase Cancer Risk
Reported December 18, 2009
(Ivanhoe Newswire) — Doses of radiation from commonly performed computed tomography (CT) scans appear to be higher than previously believed and may contribute to an estimated tens of thousands of future cancer cases.
About 70 CT scans million were performed in 2007, up from 3 million in 1980. “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 were quoted as saying. For example, a chest CT scan exposes the patient to more than 100 times the radiation dose of a routine chest X-ray. “The risks to individuals are likely to be small, but because of the large number of persons exposed annually, even small risks could translate into a considerable number of future cancers.”
Rebecca Smith-Bindman, M.D., of the University of California, San Francisco, and colleagues studied 1,119 patients undergoing 11 of the most common types of diagnostic CT scans in 2008. Using hospital records, they calculated the radiation dosage involved with each scan and then estimated lifetime risks of cancer that could be attributed to those scans.
Radiation dosage varied widely between different types of CT studies. “Within each type of CT study, effective dose varied significantly within and across institutions, with a mean [average] 13-fold variation between the highest and lowest dose for each study type,” the authors wrote.
The estimated number of CT scans that would lead to the development of one cancer case varied not only by type of CT scan but also by each patient’s age and gender. For instance, an estimated one in 270 women and one in 600 men who undergo CT coronary angiography (a heart scan) at age 40 will develop cancer as a result. One cancer case will likely occur among every 8,100 women and 11,080 men who had a routine head CT scan at the same age. “For 20-year-old patients, the risks were approximately doubled, and for 60-year-old patients, they were approximately 50 percent lower,” according to the authors.
The authors concluded, “The radiation exposure associated with CT has increased substantially over the past two decades, and efforts need to be undertaken to minimize radiation exposure from CT, including reducing unnecessary studies, reducing the dose per study and reducing the variation in dose across patients and facilities. Patient outcome studies are needed to help define when CT leads to the greatest benefit and when these studies may have no impact, where the radiation risk may be greater than the benefit expected from the examinations.”
SOURCE: Archives of Internal Medicine, December 14/28, 2009
