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Multi-Session Gamma Knife Radiosurgery Gaining Traction in North America

Wed, 09/28/2011 - 6:24am

/PRNewswire/ -- By the end of 2011, as many as nine U.S. medical centers will be offering multi-session Gamma Knife@ surgery with ExtendT to treat patients with larger tumors or lesions close to critical structures located in the brain and skull base. Extend technology allows clinicians to non-invasively immobilize the patient's head, making repeatable or multi-fraction Gamma Knife surgery feasible for these cases.

Used with Leksell Gamma Knife@ PerfexionT, the key components of Extend are patient-friendly fixation devices, such as a vacuum assisted bite block and head support with vacuum pillow. Accurate repeat fixation is ensured with a one-time use of a CT box to obtain precise stereotactic reference points, followed by repeat checks using reposition check instruments for each Gamma Knife session. Among the first U.S. centers to acquire Extend, University of Virginia (UVA, Charlottesville, Va.) physicians have employed Extend in 15 cases, mostly for benign tumors of the meninges.

"Extend is clinically advantageous for some patients because it combines Gamma Knife technology with a fractionated approach," says Jason Sheehan, M.D., Ph.D., Alumni Professor in radiation oncology and neurosurgery at UVA and co-director of UVA's Gamma Knife Center. "Specifically, you get the accuracy, precision, high dose and steep gradients of Gamma Knife surgery along with the benefits of fractionation. The true advantages of this system will become more evident as institutions begin to publish their results following its use."

Since January, clinicians at Barnes-Jewish Hospital (St. Louis, Mo.) have used Extend in Gamma Knife treatments of nine patients, five of which had recurrences of a fast-growing malignant tumor that had been previously treated with chemotherapy. In each of these cases, the lesion was too large to treat in a single session.

"For large tumors, fractionation is desirable, because large tumors will have a correspondingly larger margin of healthy tissue around them that will receive part of the dose," says Joseph R. Simpson, M.D., Ph.D., co-director of Barnes-Jewish Hospital's Gamma Knife of St. Louis. "Fractionation spares this 'halo' of normal tissue more effectively than would a high-dose single fraction. With Extend, we can conveniently apply just 7 to 8 Gy per fraction over the course of five sessions to achieve the prescribed dose."

Other targets that could benefit from a fractionated approach include lesions that abut such critical structures as the optic chiasm or that lie in "eloquent" cortex responsible for motor function or speech, according to Dr. Simpson.

"Extend gives us another 'arrow in the quiver' for treating these indications, and gives us more opportunities to use Leksell Gamma Knife Perfexion, extending the versatility of this treatment system," he adds.

Avoiding an excessive dose to a critical structure was the rationale for physicians at UW Medicine Gamma Knife Center at Harborview (Seattle, Wash.) to use Extend for the first time in July 2010.

"Our first Extend patient was a 53-year-old female with a tumor that was situated against the right optic nerve," recalls Jason Rockhill, M.D., Ph.D., Associate Professor, Department of Radiation Oncology and Neurological Surgery. "To protect this structure we used Extend to give her three Gamma Knife surgery treatments in three consecutive days."

Since then, the Gamma Knife Center has treated an additional 12 patients who had benign tumors in the meninges, pituitary or pharynx. "We're really pleased with Extend," Dr. Rockhill reports. "The patients have tolerated it quite well with the bite block. We can set up patients accurately and reliably, so the treatments have been quite efficient and the conformality is fantastic. The clinical cases have gone very smoothly."
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