Feature | November 12, 2009

Arc Therapy Matches Accuracy of Fixed-Beam in SRS, SRT

November 12, 2009 - Researchers from the University of California, Irvine Medical Center reported that image-guided RapidArc radiotherapy from Varian Medical Systems conformed to the shape and size of a targeted tumor at least as well as dynamic, fixed-beam approaches to IMRT, stereotactic radiosurgery (SRS) or stereotactic radiotherapy (SRT) for treating cancer.

"Treatment with RapidArc VMAT using a single arc produced similar dose conformality and homogeneity compared with earlier, more time-consuming approaches," said Daniel C. Schiffner, M.D., chief resident in the UCI Department of Radiation Oncology, in a presentation at the annual meeting of the American Society for Radiation Oncology (ASTRO) in Chicago.

"We found that we can deliver RapidArc treatments much more quickly, with an average of 76 percent less 'beam on' time, and also using 31 percent fewer monitor units, which could limit unintended and undesired radiation exposure to patients," said Schiffner.

The reduction in monitor units is important because it limits the degree to which patients are exposed to radiation leakage from the treatment machine, while less 'beam on' time improves clinical workflow.

Since 2008, clinicians at UC Irvine have been using Varian's Trilogy™ medical linear accelerator to treat tumors with either SRS or SRT, using a dynamic form of IMRT delivered from multiple beam angles. The department acquired RapidArc technology in early 2009, "permitting us to treat complex targets with a single arc," Schiffner said. "The technology makes it possible to dynamically shape the beam, and at the same time vary the dose delivery rate and the speed of rotation around the patient. By varying those elements, RapidArc achieves the significant time savings."

Schiffner and a team of colleagues reported on a study that compared the two treatment approaches for a total of eight patients with a total of 13 lesions.

"All of the RapidArc plans were delivered in a single arc, while IMRT plans required 7-14 fields for delivery," said Schiffner. "The clinically important advantages we saw lead us to recommend the use of image-guided RapidArc to optimize the delivery of SRS and SBRT for intracranial and extracranial targets."

Abstracts for this and other presentations and posters presented at this year's ASTRO meeting are available at the ASTRO website and also, in the "Proceedings of the American Society for Radiation Oncology 51st Annual Meeting," International Journal of Radiation Oncology, Biology, Physics, Volume 75, Issue 3, Supplement .

*One member of the UCI research team received a speaker's honorarium from Varian Medical Systems for a lecture about quality assurance processes.

For more information: www.varian.com/

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