By: Lauren Dubinsky and Gus Iversen
For hospital decision-makers, choosing between Elekta’s Gamma Knife Perfexion and one of Varian Medical Systems’ RapidArc linear accelerators for performing stereotactic radiosurgery, can be a tough call.
A new study out of Sidney Kimmel Cancer Center at Thomas Jefferson University may not provide a conclusive answer — but it does shine some light on their respective selling points.
Researchers evaluated six patients with three to four brain metastases. Each of the Gamma Knife treatment plans were designed by an experienced Gamma Knife physicist and approved by an attending neurosurgeon and radiation oncologist, and all of the RapidArc plans were developed by an experienced physicist dedicated to stereotactic radiosurgery.
“Our paper, along with other people’s publications, show that the two modalities can be used very interchangeably when [things are] done properly and correctly. The treatment efficacy should be the same,” Dr. Wenyin Shi, senior author of the study and co-director of the Jefferson Brain Tumor Program, told HCB News.
It bears mentioning that Varian co-funded the study along with the facility and that Shi and another one of the researchers, Haisong Liu, have consulting agreements with Varian. Still, the other researchers reported no conflict of interest, and the results are in line
with earlier comparisons.
They found that Gamma Knife was a little more effective than RapidArc at focusing the beam — thereby reducing the radiation exposure to healthy tissue. But they also found that the Gamma Knife procedure took roughly three to five times longer than the RapidArc procedure.
“If we are dealing with one or two metastases then the treatment time difference will probably be small, but when you are dealing with five or six or ten metastases, we are talking about 20 minutes versus two hours or longer and that is a huge difference for the patients,” said Shi.
Other studies have investigated the effectiveness of the Gamma Knife and RapidArc, but Shi said this study put more of an emphasis on the planning process — whereby the team developed a technique for radiation treatment planning to achieve optimal dose distribution.
In addition to taking longer, the Gamma Knife Perfexion requires the utilization of a minimally-invasive head frame, meaning screws must to be inserted into the patient’s scalp. Varian's RapidArc linear accelerators (TrueBeam and Edge) depend on a mapping system that makes the procedure non-invasive.
