A recent study from the prestigious medical journal, Lancet, has parents in a panic. Researchers looked at nearly 180,000 children and young adults (<22 years old) who had at least one computed tomography (CT) scan of their head between 1985 and 2002 and reviewed their medical records for the future development of cancer: http://www.thelancet.com/journals/lancet/article/PIIS0140-6736%2812%2960815-0/abstract. They found that 135 of 176,600 children developed brain tumors and 74 of 178,600 developed leukemia. Children who received an absorbed radiation dose from CT scanning of about 60 milliGray (about 2 to 3 scans) to the head had 3X the risk of brain tumors as those who received <5 milliGray. Children who received 50 milliGray from CT scans of the body had 3X the rate of leukemia: http://healthland.time.com/2012/06/07/ct-scans-in-childhood-can-triple-the-risk-of-cancer/.
Any news about increasing cancer rates in children results in widespread anxiety (if not panic) among parents. However, a deeper look may put the issue in perspective and allay some fears.
Ionizing radiation like that used by CT scanners or X-rays is well known to increase cancer risk. That risk is much higher for developing tissues, so children who are exposed to ionizing radiation are at greater risk for future development of cancer than older people. Experts will point out that the absolute risk of a child developing a brain tumor due to radiation exposure from a CT scan is low, although that’s relative. The ratio for brain cancer among children in the Lancet study (135 cases among 176,600 children) works out to roughly 1 in 1300, but that’s also over a follow-up period of 10-25 years (so the annual incidence rate is much lower than 1 in 1300). As a reference, the baseline incidence of cancer in children is about 1 in 10,000 annually. So, receiving ionizing radiation to the developing brain increases brain cancer risk, but the absolute increase from a small baseline number of cancers developing in children still remains a small number.
What is a parent to do now with this information? Most children who are recommended to have CT scans are in difficult medical situations. For instance, the child who sustains significant acute head injury as the result of a motor vehicle accident is much better served if the medical team has the information provided by a CT imaging in order to determine the severity of any potential brain injury and if/how to proceed with any medical or surgical treatment. On the other hand, parents and pediatricians should use the information in this Lancet study to lean toward imaging modalities for children that do not require ionizing radiation (ultrasound, for instance), when those options are equally (or near equally) efficacious. As with most quality medical care, communication and common sense on the part of both doctor and patient are critical.
- Patrick Maguire MD