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Occupational radiation exposure linked to left-sided brain tumors
Disproportionate reports of left-sided brain tumors in interventional physicians with sustained practices involving radiation may suggest a causal relation to occupational radiation exposure, according to study data published in the American Journal of Cardiology.
Following up on their report of nine recent cases of brain cancer in interventional cardiologists, researchers received 22 more cases from around the world.
Researchers tracked the physicians’ ages, sex, tumor types, sides involved, specialties (cardiologist vs. radiologist) and number of years in practice, based on medical records and interviews with the physicians’ patients or family.
There were 23 interventional cardiologists, two electrophysiologists and six interventional radiologists, all of whom had worked in an interventional practice with exposure to radiation. For the 26 whom career duration was known, the latency period spanned from 12 years to 32 years (mean, 23.5 ± 5.9).
There were 17 cases (55%) of glioblastoma multiforme, five meningiomas (16%) and two astrocytomas (7%). Data were available regarding the side of the brain involved in 26 operators: 22 were left-sided (85%), three right-sided and one midline in an interventional cardiologist who had performed most cases using the Sones technique, in which the head is typically centered closest to the X-ray source.
Ariel Roguin
According to Ariel Roguin, MD, PhD, study investigator with the Technion-Israel Institute of Technology, Haifa, Israel, since the publication of the paper, there has been an additional report of a left-sided astrocytoma in a 52-year-old pediatric electrophysiologist physician, making the total 32 cases.
“It is difficult to prove that the incidence of brain tumors is higher because of the ionizing radiation than in the general population. But the left-side involvement is statistically significant,” Roguin told Cardiology Today’s Intervention. “If we perform a Fisher’s exact test comparing the 22 left- vs. four non-left-sided cases to a normal expected distribution in the general population (50% for each side), then for a population of 26 subjects, the P value is .0176.”
Disclosure: Roguin reports no relevant financial disclosures.
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This is an extremely important paper and one I believe most hospitals and societies are going to try to bury. The findings fit into the category of occupational health and when you identify risks to working in a workplace, whether it's the coal mine or the cath lab, you step on all kinds of financial and egotistical feet. That is what we found in the Multispecialty Occupational Health Group: the more you go into health impact and incidence of lost time from work, the less anyone really wants you to look at it. The X-ray manufacturers don't want you to look at it because it's their design, and if you start criticizing their design, it's going to cost them money to redesign their equipment. The hospitals don't want you to look at it because they depend on young people to keep being trained as middle-aged people keep going out with health problems. And training programs don't want to talk about it because they need to train young doctors to do the same thing as the old doctors are doing. So you have a situation here where no one wants to hear the problem. And this paper really points out the consequences. Although the paper in itself does not prove anything other than identifying a cluster of cases, when you put it together with many other studies on occupational hazards, they tell a very startling story.
One of the aspects of the study I find most interesting is that cath labs and radiology suites are designed for the doctor to be on the patient's right-hand side, and so the radiation source is toward the left side of the brain; the fact that these cases are nearly all on the left side parallels the fact that the left side of the brain is being exposed the most. So, not only is this study telling you there is a clustering and there is a hypothesis to suggest why, but the sidedness strongly supports that hypothesis. So I think this is a very scary, concerning and troubling paper that everyone in health care should be talking about it. Yet the silence will be deafening.
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In their carefully documented series, Roguin and colleagues raise two important points: The incidence of primary brain tumors — especially glioblastoma — is worrisomely high, and the incidence of left-sided tumors is disproportionate. Not having a precise denominator of the number of specialists exposed makes it difficult to come up with an incidence rate. However the left-sided preponderance beats any statistical odds.
In the post-radiotherapy setting, gliomas arise with a reported 2.5% incidence at 15 years (Tsang RW. Cancer. 1993;72:2227-2233) and a relative increase in incidence of 2.6-fold vs. patients never irradiated (Ron E. N Eng J Med. 1988;319:1033-1039). The average latency of these tumors can be 9.2 to 11 years (Kaschten B. J Neurosurg. 1995;83:154-162. Nishio S. Acta Neurochir (Wien). 1998;140:763-770). No side or sex predilections are reported in literature. Despite the fact that the current paper refers to low-dose exposure, the findings are cause for a thorough review and perhaps a registry for such cases.