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Huai-che Yang, Hideyuki Kano, Nasir Raza Awan, L. Dade Lunsford, Ajay Niranjan, John C. Flickinger, Josef Novotny Jr., Jagdish P. Bhatnagar and Douglas Kondziolka

T he incidence of clinically recognized vestibular schwannomas (acoustic neuromas) is approximately 1:100,000 in the US population. 2 Because these lesions are generally benign tumors, the goals of treatment include long-term tumor control and maintenance of existing cranial nerve function. Stereotactic radiosurgery is a safe and effective tool in patients with vestibular schwannoma. 1 , 3–5 , 9 , 11 , 13–15 , 19 The role of SRS in the management of large vestibular schwannomas (> 3 cm) remains controversial. The potential for AREs and lack of rapid volume

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Hideyuki Kano, John C. Flickinger, Aya Nakamura, Rachel C. Jacobs, Daniel A. Tonetti, Craig Lehocky, Kyung-Jae Park, Huai-che Yang, Ajay Niranjan and L. Dade Lunsford

M anagement of large-volume arteriovenous malformations (AVMs) poses significant challenges to patients and physicians. For such AVMs, selected centers began to stage treatment volumes of the AVM using stereotactic radiosurgery (SRS). To date few published reports exist to validate the long-term results of this strategy. 1 , 3 , 9 , 12 , 18 , 19 The obliteration response of an AVM depends on radiation dose and volume, but for larger volumes, the dose must be reduced to decrease radiation-related brain injury. In 1992, we began to stage anatomical components of

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John C. Flickinger, Douglas Kondziolka, Ajay Niranjan and L. Dade Lunsford

cobalt sources at the time of each procedure to assess dose-rate effects. The cobalt source age varied from 0 to 9 years (median 6.3 years). We used stereotactic MR imaging for target definition in all cases. The marginal tumor dose varied from 11 to 18 Gy (median 13 Gy) and maximum dose varied from 22 to 36 Gy (median 26 Gy). The marginal tumor dose was prescribed to the 50% isodose volume in 179 patients, 40% in one patient, 55% in five patients, and 60% isodose volume in five patients. The number of isocenters used per patient varied from one to 13 (median six

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Hideyuki Kano, Ajay Niranjan, Douglas Kondziolka, John C. Flickinger and L. Dade Lunsford

option. In these patients a diagnosis was based on a combination of clinical symptoms or signs and confirmatory neuroimaging findings. All tumors extended along the course of the trigeminal nerve, showed diffuse contrast enhancement on MR imaging, and had no dural tail. Six patients underwent SRS at the time of tumor recurrence identified on imaging. Tumor progression after initial treatment was defined as an increase in lesion volume demonstrated on MR imaging. The median duration between the last excision and tumor progression was 22.1 months (range 9.4–76.5 months

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Seong-Hyun Park, Hideyuki Kano, Ajay Niranjan, John C. Flickinger and L. Dade Lunsford

Pittsburgh Medical Center. We excluded patients with neurofibromatosis, multiple meningiomas, those with fewer than 3 months of follow-up, and those whose prior surgical histology indicated that the tumor was atypical or anaplastic. Cerebellopontine angle meningiomas were defined as tumors whose maximal volume was centered at the anatomical junction of the lateral cerebellum, the pons, and the internal auditory meatus. The bulk of the tumor was superior to the jugular foramen and inferior to the trigeminal nerve. We did not include meningiomas that appeared to arise from

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L. Dade Lunsford, Ajay Niranjan, John C. Flickinger, Ann Maitz and Douglas Kondziolka

improvements in computer dose planning techniques, and improved patient selection. Although dose planning and dose selection concepts evolved between 1987 and 1992, margin dose prescriptions have remained stable for more than 10 years. The average tumor volume was 2.5 cm 3 . The median margin tumor dose was 13 Gy (range 10–20 Gy). TABLE 1 Demographics in patients undergoing GKS of VS Parameter No. (%) sex  female 417 (50.4)  male 412 (49.6) side of op  lt 416 (50.2)  rt 413 (49.8) prior op

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Douglas Kondziolka, Elad I. Levy, Ajay Niranjan, John C. Flickinger and L. Dade Lunsford

tumor margins. 7 The 50% isodose line was used to cover the tumor margin in 77 patients (78%). Image-integrated dose planning was performed using a computer workstation. The median dose delivered to the tumor margin in this series was 16 Gy (range 9–25 Gy). The median maximum tumor dose was 32 Gy (range 18–50 Gy). The lowest dose administered was for a child with a radiation-induced meningioma of the sella. Specific dose selection was based on several factors including tumor volume, surgical history, irradiation history, neurological status, tumor location, and

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Keisuke Maruyama, Douglas Kondziolka, Ajay Niranjan, John C. Flickinger and L. Dade Lunsford

two locations. The Spetzler—Martin grade 30 was II in one patient (2%), III in six (12%), and VI in 43 (86%). No patient had an AVM of Grade IV or V. A radiosurgery-based grading system score was calculated according to the following equation: AVM score = (0.1)(AVM volume in cm 3 ) + (0.02)(patient age in years) + (0.3)(location of lesion: frontal or temporal, 0; parietal, occipital, intraventricular, corpus callosum, or cerebellar, 1; or basal ganglia, thalamus, or brainstem, 2). 24 This score pursuant to the Pollock—Flickinger Scale score ranged from 0.84 to 2

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In-Young Kim, Douglas Kondziolka, Ajay Niranjan, John C. Flickinger and L. Dade Lunsford

evaluation over 1–4 years. During the period of observation, the tumors enlarged in two of these patients, and the other patient had worsened clinical symptoms. TABLE 1 Summary of clinical data in 8 patients with schwannomas originating from the oculomotor, trochlear, and abducent nerves (CNs III, IV, and VI) managed by GKS Case No. Age (yrs), Sex Schwannoma Origin (nerve) Pre-GKS Symptom Volume at GKS (cm 3 ) Marginal Dose (Gy) Radiological Outcome Progression-Free Period (mos) Clinical Follow-Up(mos) Clinical

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Ajay Niranjan, Sudesh S. Raju, Edward A. Monaco III, John C. Flickinger and L. Dade Lunsford

color online only. FIG. 2. A: GammaPlan screenshot showing dose planning ( yellow circles ) and target selection for second (right VIM) GKT. The blue circles show the volume that was irradiated at the first (left VIM) GKT. B–D: Contrast-enhanced axial T1-weighted (B) and coronal (C) and axial (D) T2-weighted FLAIR images obtained 6 months after second (right VIM) GKT. The right thalamic enhancing lesion ( dotted arrows ) is clearly seen, but the left thalamic lesion is only faintly visible ( solid arrows ). Figure is available in color online only. Follow