CT Scans Overused in Kids, Upping Lifetime Risk for Cancer

The next time that you take your daughter or son to the doctor, try to put out of your mind that the more tests done, the better. Fishing expeditions to come up with a diagnosis are all too common in medicine, and they may have adverse consequences. You might think that additional tests will allay your anxiety about what’s wrong, but CTs emit radiation, and cumulatively, it may lead to excess cancers. In many cases, they are medically unnecessary. In today’s journal JAMA Pediatrics, researchers point to widespread use of computed tomography imaging in children under age 15 and also to use of highly variable radiation doses. “The ionizing radiation doses of CT are 100 to 500 times higher than conventional radiography and are in ranges linked to an increased risk of cancer,” write the authors led by Diana L. Miglioretti, PhD, who holds a joint appointment at the University of California Davis, and Group Health Research Institute, Seattle, Washington.

CT Usage and Exposure Patterns

Reviewing use of CT imaging from seven US health care systems between 1996 and 2011, the research team found:

• In children younger than 5 years of age, CT scan use doubled between 1996 and 2005;
• In children age 5 to 14, CT use tripled;
• Even though usage stabilized between 2006 and 2007, and then began to decline, overuse  remains a key concern;
• Radiation doses used are not standardized, and in many cases, are higher than they need to be.

Estimated Cancer Risk

Next, the research team calculated organ dose (the amount of radiation absorbed by a specific organ) and effective dose (amount of radiation that the full body gets from the dose that contributes to cancer risk). “In other words,”  Miglioretti explained in an email, “doses to organs more likely to develop cancer contribute more to the effective dose.” The research team looked at abdominal/pelvic CT, chest, spine, and head CT scans.

Diana Miglioretti, PhD, the lead researcher, standing next to a CT scanner. Photo credit: UC Davis Health System, Sacramento, CA.

What is especially troubling is that the estimated risk of cancers with some scans is higher than previously reported. Here are key findings:

• “One in 300 girls younger than five years of age who undergo an abdominal/pelvis CT scan will develop a subsequent tumor,” write Alan R. Schroeder, MD, and Rita Redberg, MD, in a companion editorial titled “The Harm in Looking.”
• Likewise, CT scan of the chest is projected to result in a solid cancer in one in 330 to 480 girls.
• For spine CTs, one in 270 to 800 girls are estimated to develop a solid tumor.
• Overall, younger children are more vulnerable to radiation. In fact, younger children and girls had far higher projected risks of cancers during their lifetime than for older patients and boys.
• Children who got head CT scans before age 5 had the highest risk of leukemia, 1.9 cases per 10,000 scans, and brain cancer.

Miglioretti told Patient POV: “The radiation dose of head, abdominal, and chest CT scans was widely variable. Some kids got relatively high doses. By simply reducing the highest 25% of doses to the median dose, we may be able to prevent 43% of these cancers.” Reducing unnecessary scans also should be attempted.

More Scans Lead to More and More

Rebecca Smith-Bindman, MD, senior author of the paper, from the Department of Radiology, at University of California San Francisco, said: “You want a sense of balance. For any test, you need to ask yourself ‘Why?’ ‘Is this going to help me?’ Parents might also consider simply watching their children and deferring advanced medical imaging studies.” Most importantly, Smith-Bindman said: “Don’t go in thinking you should have your kid go through an advanced imaging study.” Doctors see that expectation and go ahead. Additionally, Smith-Bindman pointed out that the “degree to which extra studies and scans become done, it often becomes a distraction and takes away from care.” If medical imaging is medically necessary, frequently, an ultrasound will give you adequate information without adding radiation risk for your kid.

Parents need to know for starters that “doing a scan just to be safe paradoxically can do more harm,” said editorialist Alan R. Schroeder, MD, from the Department of Pediatrics at Valley Medical Center, San Jose, CA. Dr. Schroeder is also part of an effort in pediatrics to “Safely Do Less.”

“It’s also not just about radiation,” said Dr. Schroeder. “What happens next are downstream interventions.” For example, say, a kid falls and hits his head, explained Schroeder. The next thing you know, the kid has more and more scans. Dr. Schroeder also sees harm in cholesterol screening for kids. “A good proportion of kids screened will go on statins,” he said.

“Nothing less than a paradigm shift will be required if clinical medicine is to succeed in reversing overuse of tests and procedures in children,”  write Schroeder and Rita F. Redberg, MD, in the editorial, adding that our culture needs to “become more tolerant of clinical diagnoses without confirmatory imaging, more accepting of ‘watch and wait’ approaches and less accepting of the ‘another test can’t hurt’ mentality. Uncertainty can be unsettling, but it is a small price to pay for protecting ourselves and our children from thousands of preventable cancers.”

Next on Patient POV: Numerous programs and resources are available for parents and doctors, including everything from counting the radiation exposure your child is getting to questions to ask. I will put up a second post later this week that you can use for reference.

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