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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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Bruce E. Pollock and John C. Flickinger

authors have noted discrepancies between the Spetzler—Martin AVM grade and patient outcomes, especially with regard to Grade III AVMs, 3, 24 the general consensus supports this grading scale as practical and reliable. Unfortunately, this grading scale does not seem to correlate with successful AVM radiosurgery. 22, 28 This should not be surprising because the Spetzler—Martin grading system is insensitive to important factors such as AVM volume and specific location. For example, a 1-cm diameter lesion has an approximate volume of 0.6 cm 3 , whereas a 3-cm diameter

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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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Elizabeth Tyler-Kabara, Douglas Kondziolka, John C. Flickinger and L. Dade Lunsford

ventricle wall ( Fig. 1 ). After surgery the patient continued to exhibit mild neurocognitive deficits. She was referred to us for stereotactic radiosurgery to treat the residual tumor. Radiosurgery was performed using the Leksell gamma knife (Elekta Instruments, Atlanta, GA). A combination of five 14-mm isocenters was used to deliver a dose to the tumor margin of 14 Gy and a maximum dose of 28 Gy. The residual tumor volume measured 7.9 cm 3 . Subsequent imaging studies demonstrated complete regression of the contrast-enhancing tumor mass ( Fig. 1 ). Now, 53 months after

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Douglas Kondziolka, L. Dade Lunsford, Robert J. Coffey and John C. Flickinger

nine cases and multiple irradiation isocenters in 41 ( Fig. 1 ). Five isocenters of irradiation were used in four patients, and four isocenters were used in another four. Forty-four patients (88%) were treated at the 50% isodose line or greater, to take advantage of the sharp fall-off of the radiation field outside the target volume. 49 The mean dose delivered to the tumor margin was 16.98 Gy (range 10 to 25 Gy). A scatterplot of tumor volume versus dose to the margin for all 50 tumors is presented in Fig. 2 . TABLE 2 Radiosurgical dosimetry in 50 patients

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Satoshi Maesawa, John C. Flickinger, Douglas Kondziolka and L. Dade Lunsford

associated with incomplete nidus obliteration in 45 patients who underwent repeated AVM radiosurgery. 22 For a number of reasons, the residual nidus was identified outside the field (treatment volume) of the initial radiosurgery in many patients. In the remaining patients in whom the persistent nidus was within the field, no obvious cause (relative radiobiological resistance) was found. In initiating the present study, we questioned how factors associated with treatment failure at the first radiosurgery might impact on repeated radiosurgery. We hypothesized that the

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Olusola K. Ogunrinde, L. Dade Lunsford, John C. Flickinger and Douglas Kondziolka

volume was significantly associated with later preservation of useful hearing (Gardner and Robertson 13 Class I or II); useful hearing preservation was more likely with tumors averaging less than 10 mm in diameter, such as intracanalicular tumors. The present study was designed to assess the results of stereotactic radiosurgery in the management of acoustic nerve tumor patients who have useful preoperative hearing. A 2-year period was necessary to fully assess cranial nerve morbidity and to evaluate tumor control rates. Clinical Material and Methods Patient

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Costas G. Hadjipanayis, Douglas Kondziolka, John C. Flickinger and L. Dade Lunsford

Object

This study was conducted to examine the role of radiosurgery in the management of patients with recurrent or unresectable low-grade astrocytomas.

Methods

During a 13-year interval, 49 patients underwent stereotactic radiosurgery as part of multimodal treatment of their recurrent or unresectable low-grade astrocytomas. Thirty-seven of these patients (median age 14 years) harbored pilocytic astrocytomas and 12 patients harbored World Health Organization (WHO) Grade II fibrillary astrocytomas (median age 25 years). Tumors involved the brainstem in 22 cases, cerebellum in four, thalamus in six, temporal lobe in five, frontal lobe in four, and parietal lobe in three, as well as the hypothalamus, corpus callosum, insular cortex, optic tract, and third ventricle in one patient each. Each diagnosis was confirmed with the aid of stereotactic biopsy sampling in 17 patients, open biopsy sampling in five, partial resection in 13, and near-total resection in 14. Multimodal treatment included fractionated radiotherapy in 14 patients, stereotactic intracavitary irradiation in five, chemotherapy in two, cyst drainage in eight, ventriculoperitoneal shunt placement in five, and additional cytoreductive surgery in five. Tumor volumes ranged from 0.42 to 45.1 cm3. The median radiosurgical dose to the tumor margin was 15 Gy (range 9.6–22.5 Gy).

After radiosurgery, serial neuroimaging demonstrated complete tumor resolution in 11 patients, reduced tumor volume in 12, stable tumor volume in 10, and delayed tumor progression in 16. No procedure-related death was encountered. Forty-five of 49 patients are alive at a median follow-up period of 32 months after radiosurgery and 63 months after diagnosis. Sixteen patients participated in follow-up review for more than 60 months. Three patients died of local tumor progression.

Conclusions

Stereotactic radiosurgery is a potential alternative or adjunctive intervention in the management of selected patients with pilocytic or WHO Grade II fibrillary astrocytomas, usually performed for small-volume tumors in an attempt to avoid larger-field fractionated radiotherapy.

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Douglas Kondziolka, L. Dade Lunsford, John C. Flickinger and John R. W. Kestle

, axial short- and long-TR images are obtained at 3-mm image intervals. In patients with small malformations (less than 15 mm in diameter), a volume acquisition is performed with images at 1-mm intervals. After the administration of a contrast agent, repeat axial and coronal short-TR images are obtained. The dimensions of the malformation are measured in three planes. Although we acknowledge that definition of the cavernous malformation nidus is difficult, we define the malformation as the region characterized by mixed signal change within an outer hemosiderin ring

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L. Dade Lunsford, Salvador Somaza, Douglas Kondziolka and John C. Flickinger

patients had outpatient conventional fractionated external-beam radiation therapy. The radiation volume was based on CT or MR definition of the tumor volume plus a margin of 2 to 3 cm. The median radiotherapy dose was 56 Gy (range 45 to 60 Gy) and the median dose per fraction was 1.8 Gy. The median number of fractions was 31 (range 22 to 36), delivered over a median time of 5.5 weeks. Because of subsequent neoplastic cyst formation, two patients also underwent intracavitary irradiation with a colloidal suspension of radioactive phosphorus-32. Cyst volumes were