|
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 |
