Leg Shields May Prevent Radiation-Induced DNA Damage During EVAR

Operators who perform endovascular aneurysm repair (EVAR) experience routine DNA damage as a result of exposure to radiation, a new study suggests. While the clinical significance of the genetic damage is unclear, the researchers found that it is reversible and can be avoided by adding leg shields to standard radiation protection gear.

The type of genetic damage demonstrated in the study involves breakage of strands of DNA, said Norman J. Kleiman, PhD (Columbia University Mailman School of Public Health, New York, NY), who was not involved in the study. He told TCTMD that it stands to reason that detectable cell damage like the kind seen in the EVAR operators suggests the potential for mutation that can lead to cancers and other radiation-related disease. While the risk is likely small and difficult to quantify, he said, the message for those performing EVAR procedures is to think about their cumulative exposures on the job.

“In the scheme of things, the advice to operators is when possible wear leg shields. If it’s practical and it’s available, this study suggests that it’s probably prudent to do so,” Kleiman said. “Is this a huge risk? Probably not. Can I tell you that with certainty? No, because you would need to enroll literally thousands of physicians and follow them for 50 years.”

Biomarkers Increased Post-EVAR, but Not After Surgery

In the study, published online October 20, 2017, ahead of print in Circulation, researchers led by Tamer El-Sayed, MRCS (King’s College London, England), used molecular and cellular techniques to look for DNA damage in the blood of 15 vascular surgeons and interventional radiologists before, immediately after, and 24 hours after they performed EVAR or open aortic repairs. The sampling occurred over a total of 45 procedures. Six operators were asked to wear leg shields as additional protection during some cases. All operators also wore personal dosimeters.

Compared with open repair, EVAR procedures were significantly longer and had higher dose area product.

Immediately after EVAR procedures, blood sampling showed increases in two cellular biomarkers—phosphorylated ataxia telangiectasia mutated and gamma-H2AX—in the circulating lymphocytes. No such increases were seen in operators after open surgical repair.

When biomarkers were evaluated in the operators asked to wear leg shields, no increase was seen after procedures in which they were worn. Dosimeters provided confirmation of scatter radiation to the legs that was higher than the dose measured at chest level. For all operators, the DNA damage showed evidence of repair by 24 hours.

Variations in Susceptibility

According to Kleiman, while the biomarkers indicate breaks in strands of DNA, this type of damage actually occurs frequently in all of us.

“This happens every day, all the time from all kinds of things, including just breathing oxygen,” he noted. “Free radicals are created all the time . . . on the order of as much as a million per day, and the cells are really well-primed to deal with it.”

An important factor that cannot be quantified, yet factors heavily into the equation, is individual response to radiation exposures. El-Sayed and colleagues sought to elucidate this by exposing some of the blood samples to steady levels of in vitro irradiation. They found considerable variation from operator to operator in the amount of detectable DNA damage.

“We know that there is differential sensitivity, and hopefully we can apply that to future efforts in the area of protection,” Kleiman observed.

Importantly, El-Sayed and colleagues note that EVAR exposes operators to radiation doses that are nearly six times as high as those interventional cardiologists receive when performing PCI.

“Operators often neglect to wear lower-leg lead shielding, viewing its use as cumbersome and unnecessary, but the present data highlight the importance of protecting the legs,” they conclude.