Radiation-induced cancers have tripled in the last two decades and diagnostic imaging has already been admitted as a cause by the U.S. government. According to a study of seven U.S. healthcare systems, the use of computed tomography (CT) scans of the head, abdomen/pelvis, chest or spine, in children younger than age 14 more than doubled from 1996 to 2005, and this associated radiation is projected to potentially increase the risk of radiation-induced cancer in these children in the future, according to a study published Online First by JAMA Pediatrics.
The use of CT in pediatrics has increased over the last two decades. The ionizing radiation doses delivered by the tests are higher than convention radiography and are in ranges that have been linked to an increased risk of cancer. Children are more sensitive to radiation-induced carcinogenesis and have many years of life left for cancer to develop, the authors write in the study background.
"The increased use of CT in pediatrics, combined with the wide variability in radiation doses, has resulted in many children receiving a high-dose examination," the study notes.
The Food and Drug Administration (FDA) has warned radiologists in the past that the scan expose children to doses of radiation far greater than is safe for their age and weight -- by some estimates, up to six times more than what is needed to produce clear images.
In a public health notification, FDA officials warned recently that, despite earlier efforts by the American College of Radiology to warn doctors to reduce radiation levels when imaging children, the problem still exists.
Currently, 75 million CT scans are performed annually in the United States, around half in women, reflecting the large number of individuals who are exposed to this source of radiation. Thought leaders in radiology are often quoted as estimating that 30% or more of advanced imaging tests may be unnecessary, and while there are few scientific data to precisely estimate the amount of overuse, many radiologists believe the proportion may be even higher.
Diana L. Miglioretti, Ph.D., of the Group Health Research Institute and University of California, Davis, and colleagues quantified trends in the use of CT in pediatrics plus the associated radiation exposure and estimated potential cancer risk using data from seven U.S. health care systems.
The authors note the use of CT doubled for children younger than 5 years old and tripled for children 5 to 14 years of age between 1996 and 2005 before remaining stable between 2006 and 2007 and then beginning to decline.
The projected lifetime attributable risks of solid cancer were higher for younger patients and girls than for older patients and boy. The risks were also higher for patients who underwent CT scans of the abdomen/pelvis or spine than for patients who underwent other types of CT scans, according to the results.
The estimates also suggest that for girls, a radiation-induced solid cancer is projected to potentially result from every 300 to 390 abdomen/pelvis scans, 330 to 480 chest scans, and 270 to 800 spine scans, depending on age. The potential risk of leukemia was highest from head scans for children younger than 5 years of age at a rate of 1.9 cases per 10,000CT scans, the results show.
Developing radiation-induced cancer is at higher risk for children. The reason is children are much more sensitive to radiation because of the way their cells divide. Their DNA is much more susceptible to damage. While the risk of an adult developing cancer from a CT scan is about 1 in 2000, for a child the risk goes up to 1 in 500. Compounding the problem, it's not always easy to tell when a CT scan's levels are in the danger zone.
When radiation levels are too high on traditional X-rays, images appear overexposed; it's easy to see that something is wrong. With CT scans, the picture is so good it's not likely to be compromised, even when radiation levels are way above normal, according to the American College of Radiology.
"This is one reason that many centers don't even recognize that there is a problem," said Kevin Roche, a pediatric radiologist at New York University Medical Center.
The authors estimate that 4,870 future cancers could be caused by the 4 million pediatric CT scans performed each year. Based on their calculations, the authors also suggest that reducing the highest 25 percent of doses to the median (midpoint) may prevent 43 percent of these cancers, the authors suggest.
"Thus, more research is urgently needed to determine when CT in pediatrics can lead to improved health outcomes and whether other imaging methods (or no imaging) could be as effective. For now, it is important for both the referring physician and the radiologist to consider whether the risks of CT exceed the diagnostic value it provides over other tests, based on current evidence," the study concludes.
Intense marketing focusing on profit leads to the rapid purchase of machines prior to completely understanding how this technology should be used to improve health outcomes has created excess capacity, complicated by few evidence-based guidelines for its use.
Strong financial incentives, reflected by the growing ownership of CT scanners by nonradiologists for use in their private medical offices, strong patient demand (in part resulting from direct-to-consumer advertisements that do not mention untoward effects), and medical malpractice concerns leading to defensive test ordering have all further contributed to high excess use.
Findings from the Institute of Medicine (IOM) have found that CT (computed tomography) scans are a major cause of the breast cancer they are supposed to detect, and women should avoid all ‘just-in-case’ and routine screening, a US government report concluded.
"Developing tissues in children are more sensitive to radiation and their longer expected life spans also allows additional time for the emergence of detrimental effects," says co-author, Reza Fazel, M.D., M.Sc., a cardiologist at the Emory School of Medicine.
Dr. Steven Krug, emergency department chief at Chicago's Children's Memorial Hospital, said many institutions including his own have started using ultrasound to diagnose appendicitis in some kids with abdominal pain. Ultrasound images aren't as detailed as CT images, and children with uncertain results will still need CT scans, but he said the trend may help limit radiation exposure.
"Irradiation of the brain with dose levels overlapping those imparted by CT can, in at least some instances, adversely affect intellectual development," says Dr. Per Hall from the Karolinska Institute in Stockholm Hall.
April McCarthy is a community journalist playing an active role reporting and analyzing world events to advance our health and eco-friendly initiatives.