Multiple CT scans in kids linked to later cancer risk

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By Linda Carroll

Over the last two decades CT scans in children have skyrocketed and the radiation from the CT procedures could result in thousands of future cases of cancer, according to a large, multi-center study published Monday. But cutting unnecessary scans and lowering the dose level for kids could reduce the risk by as much as 62 percent.

While CT scans provide “beautiful 3-D pictures of the inside of the body,” they also subject patients to a significant amount of radiation, which may boost the risk of future cancer, said the study’s lead author Diana Miglioretti, a professor of biostatistics at the University of California, Davis, and a senior investigator at the Group Health Research Institute.

Between 1996 and 2006 CT scans in children under age 5 nearly doubled, while they almost tripled in kids aged 5 to 14 years, according to the report in JAMA Pediatrics. While the number of scans in children has declined since 2006, it’s still much higher than in 1996.

While the researchers suspect many of those scans could be avoided, for some kids, like 5-year-old Dezhan Frajer, the clearer 3D images that come from CT are the only way to figure out what’s wrong. Dezhan has been suffering from some complicated ear and eye symptoms, and his mom, Tamika is hoping his scans will explain what’s going on.

CT scans are often used in kids when appendicitis is suspected or to rule out severe damage when children hit their heads hard or if there is concern that the spine has been injured. They are also used to diagnose brain tumors and other abnormalities.

CT scans became more popular because, “it is a great tool and is very sensitive and accurate,” Miglioretti said.

Miglioretti and her colleagues scrutinized data from six large HMOs. Included in the study were data from 152,419 to 371,095 children each year. They found CT scan use jumped between 1996 and 2005, remained stable until 2007, and then started to decline.

Even with the decline, in 2010 scans were still being done at nearly two and a half times the rate of 1996 in children aged 5 to 14 and one-and-a-half times the 1996 rate in children under age 5.

The researchers then plugged the CT scan rates into a model that predicts cancer rates based on data from a number of sources, including those from Japanese atomic bomb survivors.

An additional 4,870 cancers that could be traced to CT scan radiation absorbed by children, they found.

That amounts to approximately one cancer in 1,000 people, said Andrew Maidment, an associate professor of radiology and chief of physics at the University of Pennsylvania. To put that number in perspective, Maidment said, the lifetime risk of getting cancer is 448 in 1,000. So, if the model is right, the added risk due CT radiation exposure would bump the number up from 448 to 449.

Parents whose kids need a CT scan shouldn’t be unduly worried, Maidment said, adding the average radiation dose from the procedure in adults is 3 to 8 millisieverts.

“To give you an idea of what that means, the background radiation a person on the East Coast receives in a year is about 3 millisieverts, while it’s around 20 millisieverts among people living at higher altitudes [like Denver],” he said.

Still, Maidment said, parents should talk to their children’s doctors and make sure a CT is necessary and that no other scanning method will do.

One example is the diagnosis of appendicitis in kids, for which doctors often choose a CT scan. Often an ultrasound is enough to catch the problem, with a backup of a CT scan if the ultrasound isn’t definitive.

Although the new study provides only an estimate of how many cancers might result from radiation from CT scans, “when it comes to our children we should be better safe than sorry until we can prove that this is safe. We need to be very careful with our kids,” Miglioretti said.

For Dezhan’s physician, pediatric radiologist Dr. Raymond Sze, there are several questions that should be asked before a CT is ordered.

“Will it allow earlier diagnosis?” said Sze, chief of the division of diagnostic imaging and radiology at the Children’s National Medical Center in Washington, D.C., and a professor of radiology and pediatrics at the George Washington University School of Medicine and Health Sciences. “Will it avoid surgery? Will it allow us to avoid other unnecessary procedures as well?”