The option of Linac-based radiosurgery in a Gamma Knife radiosurgery center

Objective: Due to the fundamental differences in treatment delivery, linear-accelerator-based radiosurgery can be complementary to Gamma Knife (GK) for intracranial lesions. We reviewed the effect of adding GK to an existing linear accelerator (Linac)-based radiosurgery practice and analyzed case selections for the two modalities. Patients and methods: UC Davis Medical Center installed a Leksell Gamma Knife Model C in October 2003 to supplement an established Linac-based radiosurgery program. Radiosurgery indications for the 15 months before and after installation were compared. Results: Radiosurgery cases expanded by twofold from 68 patients before GK installation to 139 after, with 106 treated by GK and 33 by Linac. Besides a major increase for trigeminal neuralgia and a general growth for acoustic neuroma, meningioma and brain metastases, case numbers for glioma and arteriovenous malformation (AVM) remained stable. Considering case selections for Linac, glioma decreased from 28 to 18%, while meningioma and metastases increased from 9 to 21% and 38-46%, respectively. The Linac patients receiving fractionated treatment also increased from 37 to 61%. Conclusions: While the majority of patients were treated with GK, a significant proportion was judged to be suited for Linac treatment. This latter group included particularly patients who benefit from fractionated therapy.