Introduction | Clinical Explanation | Journal Article by Dr. Christopher Duma

Leading Edge

Journal article by Dr. Christopher Duma

The Role of MRI and Proton MRS in Directing “Leading Edge” Boost Gamma Knife Radiosurgery for Recurrent Glioblastoma Multiforme

By: Duma CM; Brant-Zawadzki M; Shea WM; Tassin J; Mackintosh R; Plunkett M; and Sharp S

Departments of Neurosurgery, Radiology and Radiation Oncology at Hoag Memorial Hospital Presbyterian in Newport Beach, California.

Purpose: Glioblastoma multiforme (GBM) defies any therapy because the tumor cannot be effectively treated locally. White matter infiltration of tumor cells, beyond gadolinium-enhancing tumor mass is the rule. Studies have suggested that FLAIR sequences are most sensitive to tumor, and that Proton MRS improves specificity of tumor detection within, and even beyond FLAIR-positive zones. When conventional involved field radiation therapy is used, survival times historically are approximately 6 mo. for patients with recurrent disease. We targeted “leading edge” zones defined by FLAIR and MRS with boost stereotactic radiosurgery to determine its effect on survival.

Methods: Seventeen consecutive patients with recurrent GBM amenable to “leading edge” Gamma Knife radiosurgery (GKRS) were treated over a 3.5-year interval using MRS- and/or FLAIR-directed isodose planning. Patient age ranged from 21-77, median: 49. Treatment isodose plans were prescribed to include either MR Spect or FLAIR signal abnormalities. Treatment volumes averaged 26 cc (3.7 cm average diameter.) Median minimum target dose was 12 Gy at the 50% isodose line. Infratentorial, basal ganglia or brainstem tumors were excluded. All patients had undergone involved-field radiation therapy before GKRS treatment. Twelve patients received immunotherapy as part of an ongoing trial, and seven patients received chemotherapy.

Results: The median follow-up interval was 10 mos. Median survival for patients with recurrent disease from time of GKRS boost was also 14 mos. Survivals ranged from 0.25 to 27+ mos. Neither chemotherapy nor immunotherapy appeared to affect results. Seven patients (26%) had treatable radiosurgery-induced edema, MRS proving useful in differentiating necrosis from tumor in these cases.

Conclusion: Considering patients in this series were negatively selected (most patients had evidence of tumor crossing into or across the corpus callosum) there appears to be a survival advantage using FLAIR- or MR Spect-directed “leading edge” GKRS for patients with recurrent GBM.

For more information, e-mail us at GammaKnife@hoaghospital.org or call 866/446-2445

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