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Winter 2012

Gamma Knife Radiosurgery Extends Its Reach

As the technology and techniques for stereotactic radiosurgery have evolved, they have improved the prognoses for many complex neurological disorders, from brain tumors to epilepsy, trigeminal neuralgia and arteriovenous malformations (AVMs).

Dr. Michael McDermott

Michael McDermott, M.D., co-director of the Gamma Knife Radiosurgery Program at UCSF Medical Center, is excited by the latest advances.

"The Extend frame Leksell Gamma Knife Perfexion enables fractionated treatments and volume staging," McDermott says. "It enables us to treat larger lesions or those in more sensitive locations than we could treat before. The Perfexion system also allows us to treat tumors in the paranasal sinuses, orbits and upper cervical spine."

Advancing Brain Tumor Treatment

In the 20 years since UCSF became the first program in Northern California to adopt the Gamma Knife in 1991, it has treated more than 3,400 patients.

"As the indications for Gamma Knife surgery have expanded and as our volumes have increased, we've developed a careful process for weighing the risks and benefits of radiosurgery versus other treatment options," McDermott says. "We use a regular, multidisciplinary radiosurgery conference to analyze the medical concerns and then offer our patients informed choices."

MRI

In the case of brain tumors, the UCSF neurosurgery team will consider radiosurgery an option for treating malignancies such as chordomas and chondrosarcomas, as well as benign tumors such as meningiomas and schwannomas.

"Because this new Extend frame system can safely deliver doses to volumes we couldn’t previously complete, we plan to establish protocols for a variety of tumors," McDermott says. The neurosurgery team has begun lining up clinical studies to document outcomes.

Arteriovenous Malformations

The team has also instituted a successful program of volume-stage, fractionated radiosurgery for large AVMs.

"Some AVMs are too large for a single session treatment," McDermott says. "In the past, to avoid complications we had to drop the dose. But now we can deliver doses to separate, smaller portions of a large AVM over time — so-called volume staging — and thus we can deliver higher doses with more precision. The program we have developed allows us to deliver these volume-staged treatments while avoiding overlap in normal tissues."

In many cases, this approach has been able to convert unacceptably high surgical risks to acceptable risks, and patients have done very well with the combination of treatments.

"Our vascular neurosurgeons love operating on these cases because the radiosurgery thickens the walls of AVM vessels," McDermott says.

Another benefit of the Extend frame system is patient comfort. Radiosurgery has long had the advantage of only minor discomfort and rapid recuperation. But now, McDermott adds, "We don't even need pins through the skin, just a bite block and a custom-conformed headrest with a relocatable frame."

For more information, contact Dr. Michael McDermott at (415) 353-7500.

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