scholarly journals Dosimetric effects of Onyx embolization on Gamma Knife arteriovenous malformation dose distributions

2016 ◽  
Vol 125 (Supplement_1) ◽  
pp. 114-122 ◽  
Author(s):  
David J. Schlesinger ◽  
Håkan Nordström ◽  
Anders Lundin ◽  
Zhiyuan Xu ◽  
Jason P. Sheehan
Keyword(s):  
Gamma Knife ◽  
Radiation Effects ◽  
Gamma Knife Radiosurgery ◽  
Dose Calculation ◽  
Clinical Results ◽  
Detectable Effect ◽  
Dose Distributions ◽  
Passing Rates ◽  
Dose Metrics ◽  
The Mean

OBJECTIVEPatients with arteriovenous malformations (AVMs) treated with Gamma Knife radiosurgery (GKRS) subsequent to embolization suffer from elevated local failure rates and differences in adverse radiation effects. Onyx is a common embolic material for AVMs. Onyx is formulated with tantalum, a high atomic number (Z = 73) element that has been investigated as a source of dosimetric uncertainty contributing to the less favorable clinical results. However, prior studies have not modeled the complicated anatomical and beam geometries characteristic of GKRS. This study investigated the magnitude of dose perturbation that can occur due to Onyx embolization using clinically realistic anatomical and Gamma Knife beam models.METHODSLeksell GammaPlan (LGP) was used to segment the AVM nidus and areas of Onyx from postcontrast stereotactic MRI for 7 patients treated with GKRS postembolization. The resulting contours, skull surface, and clinically selected dose distributions were exported from LGP in DICOM-RT (Digital Imaging and Communications in Medicine–radiotherapy) format. Isocenter locations and dwell times were recorded from the LGP database. Contours were converted into 3D mesh representations using commercial and in-house mesh-editing software. The resulting data were imported into a Monte Carlo (MC) dose calculation engine (Pegasos, Elekta Instruments AB) with a beam geometry for the Gamma Knife Perfexion. The MC-predicted dose distributions were calculated with Onyx assigned manufacturer-reported physical constants (MC-Onyx), and then compared with corresponding distributions in which Onyx was reassigned constants for water (MC-water). Differences in dose metrics were determined, including minimum, maximum, and mean dose to the AVM nidus; selectivity index; and target coverage. Combined differences in dose magnitude and distance to agreement were calculated as 3D Gamma analysis passing rates using tolerance criteria of 0.5%/0.5 mm, 1.0%/1.0 mm, and 3.0%/3.0 mm.RESULTSOverall, the mean percentage differences in dose metrics for MC-Onyx relative to MC-water were as follows; all data are reported as mean (SD): minimum dose to AVM = −0.7% (1.4%), mean dose to AVM = 0.1% (0.2%), maximum dose to AVM = 2.9% (5.0%), selectivity = 0.1% (0.2%), and coverage = −0.0% (0.2%). The mean percentage of voxels passing at each Gamma tolerance were as follows: 99.7% (0.1%) for 3.0%/3.0 mm, 98.2% (0.7%) for 1.0%/1.0 mm, and 52.1% (4.4%) for 0.5%/0.5 mm.CONCLUSIONSOnyx embolization appears to have a detectable effect on the delivered dose distribution. However, the small changes in dose metrics and high Gamma passing rates at 1.0%/1.0 mm tolerance suggest that these changes are unlikely to be clinically significant. Additional sources of delivery and biological uncertainty should be investigated to determine the root cause of the observed less favorable postembolization GKRS outcomes.

scholarly journals OS8.3 Gamma knife radiosurgery for large meningiomas: 10 years of experience

2019 ◽  
Vol 21 (Supplement_3) ◽  
pp. iii16-iii16
Author(s):  
K Abdel Karim ◽  
A El-Shehaby ◽  
W Reda ◽  
R Emad Eldin ◽  
A Nabeel ◽  
...  
Keyword(s):  
Gamma Knife ◽  
Radiation Effects ◽  
Gamma Knife Radiosurgery ◽  
Long Term Results ◽  
Tumor Control ◽  
Safe Treatment ◽  
Intracranial Meningiomas ◽  
Prescription Dose ◽  
The Mean

Abstract BACKGROUND The use of gamma knife radiosurgery for the treatment of intracranial meningiomas has been established as an effective and safe treatment modality. Larger meningiomas are typically managed by surgery followed by radiosurgery. For situations where patients are not amenable to surgery fractionated stereotactic radiotherapy is the traditionally suggested treatment. Treatment of large meningiomas (usually defined as >10 cc) by stereotactic radiosurgery has been investigated in some recent reports, either by single-session, volume-staged or hypofractionation technique. However, there are no long-term results. The purpose of this study is to assess the long-term efficacy and safety of gamma knife radiosurgery for large (15 cc or more) intracranial meningiomas. MATERIAL AND METHODS In this study we included 80 patients with large meningiomas (³ 15 cc) who were followed up for more than 5 years. Non-benign meningiomas were excluded. Also, meningiomatosis and NF2 patients were not included. There were 18 males (22.5%) and 62 females (77.5%). The mean age was 46 years (20–83 years). Twenty-six patients (32.5%) had previous surgery. Tumor were supratentorial in 14 (17.5%) patients and skull base in 66 (82.5%) patients. The mean tumor volume was 22.3 cc (15–57.3 cc). The mean prescription dose was 11 Gy (9–12 Gy). RESULTS The mean follow up period was 8.4 years (5–17 years). The tumor shrank in 43 patients (54%), was stable in 30 patients (37%) and progressed in 7 patients (8%). The tumor control rate was 91%. Adverse radiation effects were observed in 11 patients (14%) but only 5 (6.5%) were symptomatic. These were temporary in all cases. CONCLUSION Gamma knife radiosurgery provides an effective and safe treatment option for large meningiomas. Low margin dose appears to be sufficient for tumor control. Surgery remains the first option in these cases.

scholarly journals Low Dose Gamma-knife Radiosurgery for Diffuse Brainstem Gliomas

2018 ◽  
Vol 25 (3) ◽  
pp. 217-225
Author(s):  
Julio C. Antico ◽  
Daniel Benzecry Almeida
Keyword(s):  
Effective Treatment ◽  
Gamma Knife ◽  
Tumor Size ◽  
Radiation Effects ◽  
Gamma Knife Radiosurgery ◽  
Prescription Dose ◽  
Brainstem Tumors ◽  
The Mean ◽  
Early Late

Introduction: Diffuse brainstem glial tumors remain a challenge. Despite many advances in neurosurgical techniques, no effective treatment is currently available. Recently, some authors showed beneficial results with gamma-knife radiosurgery (GK) for focal brainstem tumors. Objective: to analyze safety and effectiveness of GK in patients with diffuse brainstem gliomas. Methods: Eleven patients with diffuse brainstem gliomas treated with Gamma-knife from November 2001 to June 2009 were included. Complete data such as age, gender, symptoms, tumor size, prescription dose, adverse radiation effects and an early late follow-up were analyzed. Results: The mean age was 28.7 years (ranging from 1y 7m to 62y). Six patients were female and 5 were male. The gamma-knife prescription dose ranged from 6 to 7 Gy. All patients had clinical and imaging improvement at an early follow-up, although in 6, there was a late increase in tumor size and death. The others remained clinically stable or better. Larger tumors had a direct relationship with a poorer prognosis. No patient developed complications related to the radiosurgical treatment. Conclusion: Gamma-Knife is a safe and effective treatment for selected patients with diffuse brainstem tumors. The authors propose lower doses. Further studies are mandatory in order to analyze which patients could benefit from this treatment.

Survival and outcomes in patients with ≥ 25 cumulative brain metastases treated with stereotactic radiosurgery

2021 ◽  
pp. 1-11
Keyword(s):  
Brain Metastases ◽  
Stereotactic Radiosurgery ◽  
Gamma Knife ◽  
Radiation Effects ◽  
Univariate Analysis ◽  
Survival Rates ◽  
Gamma Knife Radiosurgery ◽  
Cumulative Number ◽  
Study Results ◽  
The Mean

OBJECTIVE In the era in which more patients with greater numbers of brain metastases (BMs) are being treated with stereotactic radiosurgery (SRS) alone, it is critical to understand how patient, tumor, and treatment factors affect functional status and overall survival (OS). The authors examined the survival outcomes and dosimetry to critical structures in patients treated with Gamma Knife radiosurgery (GKRS) for ≥ 25 metastases in a single session or cumulatively over the course of their disease. METHODS A retrospective analysis was conducted at a single institution. The institution’s prospective Gamma Knife (GK) SRS registry was queried to identify patients treated with GKRS for ≥ 25 cumulative BMs between June 2013 and April 2020. Ninety-five patients were identified, and their data were used for analysis. Treatment plans for dosimetric analysis were available for 89 patients. Patient, tumor, and treatment characteristics were identified, and outcomes and OS were evaluated. RESULTS The authors identified 1132 patients with BMs in their institutional registry. Ninety-five patients were treated for ≥ 25 cumulative metastases, resulting in a total of 3596 tumors treated during 373 separate treatment sessions. The median number of SRS sessions per patient was 3 (range 1–12 SRS sessions), with nearly all patients (n = 93, 98%) having > 1 session. On univariate analysis, factors affecting OS in a statistically significant manner included histology, tumor volume, tumor number, diagnosis-specific graded prognostic assessment (DS-GPA), brain metastasis velocity (BMV), and need for subsequent whole-brain radiation therapy (WBRT). The median of the mean WB dose was 4.07 Gy (range 1.39–10.15 Gy). In the top quartile for both the highest cumulative number and highest cumulative volume of treated metastases, the median of the mean WB dose was 6.14 Gy (range 4.02–10.15 Gy). Seventy-nine patients (83%) had all treated tumors controlled at last follow-up, reflecting the high and durable control rate. Corticosteroids for tumor- or treatment-related effects were prescribed in just over one-quarter of the patients. Of the patients with radiographically proven adverse radiation effects (AREs; 15%), 4 were symptomatic. Four patients required subsequent craniotomy for hemorrhage, progression, or AREs. CONCLUSIONS In selected patients with a large number of cumulative BMs, multiple courses of SRS are feasible and safe. Together with new systemic therapies, the study results demonstrate that the achieved survival rates compare favorably to those of larger contemporary cohorts, while avoiding WBRT in the majority of patients. Therefore, along with the findings of other series, this study supports SRS as a standard practice in selected patients with larger numbers of BMs.

Gamma Knife Radiosurgery for Cerebellopontine Angle Meningiomas

Neurosurgery ◽  
2014 ◽  
Vol 75 (4) ◽  
pp. 398-408 ◽  
Author(s):  
Dale Ding ◽  
Robert M. Starke ◽  
Hideyuki Kano ◽  
Peter Nakaji ◽  
Gene H. Barnett ◽  
...  
Keyword(s):  
Tumor Progression ◽  
Gamma Knife ◽  
Cerebellopontine Angle ◽  
Radiation Effects ◽  
Gamma Knife Radiosurgery ◽  
Neurological Deterioration ◽  
Multicenter Cohort Study ◽  
Presenting Symptoms ◽  
The Mean

Abstract BACKGROUND: Resection of cerebellopontine angle (CPA) meningiomas may result in significant neurological morbidity. Radiosurgery offers a minimally invasive alternative to surgery. OBJECTIVE: To evaluate, in a multicenter cohort study, the outcomes of patients harboring CPA meningiomas who underwent Gamma Knife radiosurgery (GKRS). METHODS: From 7 institutions participating in the North American Gamma Knife Consortium, 177 patients with benign CPA meningiomas treated with GKRS and at least 6 months radiologic follow-up were included for analysis. The mean age was 59 years and 84% were female. Dizziness or imbalance (48%) and cranial nerve (CN) VIII dysfunction (45%) were the most common presenting symptoms. The median tumor volume and prescription dose were 3.6 cc and 13 Gy, respectively. The mean radiologic and clinical follow-up durations were 47 and 46 months, respectively. Multivariate regression analyses were performed to identify the predictors of tumor progression and neurological deterioration. RESULTS: The actuarial rates of progression-free survival at 5 and 10 years were 93% and 77%, respectively. Male sex (P = .014), prior fractionated radiation therapy (P = .010), and ataxia at presentation (P = .002) were independent predictors of tumor progression. Symptomatic adverse radiation effects and permanent neurological deterioration were observed in 1.1% and 9% of patients, respectively. Facial spasms at presentation (P = .007) and lower maximal dose (P = .011) were independently associated with neurological deterioration. CONCLUSION: GKRS is an effective therapy for CPA meningiomas. Depending on the patient and tumor characteristics, radiosurgery can be an adjuvant treatment to initial surgical resection or a standalone procedure that obviates the need for resection in most patients.

Gamma knife radiosurgery in the management of cavernous sinus meningiomas

2000 ◽  
Vol 93 (supplement_3) ◽  
pp. 68-73 ◽  
Author(s):  
Pierre-Hugues Roche ◽  
Jean Régis ◽  
Henry Dufour ◽  
Henri-Dominique Fournier ◽  
Christine Delsanti ◽  
...  
Keyword(s):  
Mr Imaging ◽  
Tumor Growth ◽  
Gamma Knife ◽  
Cavernous Sinus ◽  
Gamma Knife Radiosurgery ◽  
Surgical Removal ◽  
Content Type ◽  
Cavernous Sinus Meningioma ◽  
The Mean ◽  
Fine Print

Object. The authors sought to assess the functional tolerance and tumor control rate of cavernous sinus meningiomas treated by gamma knife radiosurgery (GKS). Methods. Between July 1992 and October 1998, 92 patients harboring benign cavernous sinus meningiomas underwent GKS. The present study is concerned with the first 80 consecutive patients (63 women and 17 men). Gamma knife radiosurgery was performed as an alternative to surgical removal in 50 cases and as an adjuvant to microsurgery in 30 cases. The mean patient age was 49 years (range 6–71 years). The mean tumor volume was 5.8 cm3 (range 0.9–18.6 cm3). On magnetic resonance (MR) imaging the tumor was confined in 66 cases and extensive in 14 cases. The mean prescription dose was 28 Gy (range 12–50 Gy), delivered with an average of eight isocenters (range two–18). The median peripheral isodose was 50% (range 30–70%). Patients were evaluated at 6 months, and at 1, 2, 3, 5, and 7 years after GKS. The median follow-up period was 30.5 months (range 12–79 months). Tumor stabilization after GKS was noted in 51 patients, tumor shrinkage in 25 patients, and enlargement in four patients requiring surgical removal in two cases. The 5-year actuarial progression-free survival was 92.8%. No new oculomotor deficit was observed. Among the 54 patients with oculomotor nerve deficits, 15 improved, eight recovered, and one worsened. Among the 13 patients with trigeminal neuralgia, one worsened (contemporary of tumor growing), five remained unchanged, four improved, and three recovered. In a patient with a remnant surrounding the optic nerve and preoperative low vision (3/10) the decision was to treat the lesion and deliberately sacrifice the residual visual acuity. Only one transient unexpected optic neuropathy has been observed. One case of delayed intracavernous carotid artery occlusion occurred 3 months after GKS, without permanent deficit. Another patient presented with partial complex seizures 18 months after GKS. All cases of tumor growth and neurological deficits observed after GKS occurred before the use of GammaPlan. Since the initiation of systematic use of stereotactic MR imaging and computer-assisted modern dose planning, no more side effects or cases of tumor growth have occurred. Conclusions. Gamma knife radiosurgery was found to be an effective low morbidity—related tool for the treatment of cavernous sinus meningioma. In a significant number of patients, oculomotor functional restoration was observed. The treatment appears to be an alternative to surgical removal of confined enclosed cavernous sinus meningioma and should be proposed as an adjuvant to surgery in case of extensive meningiomas.

Gamma knife radiosurgery for craniopharyngiomas

2000 ◽  
Vol 93 (supplement_3) ◽  
pp. 47-56 ◽  
Author(s):  
Wen-Yuh Chung ◽  
David Hung-Chi Pan ◽  
Cheng-Ying Shiau ◽  
Wan-Yuo Guo ◽  
Ling-Wei Wang
Keyword(s):  
Clinical Outcome ◽  
Gamma Knife ◽  
Tumor Volume ◽  
Gamma Knife Radiosurgery ◽  
Tumor Control ◽  
Content Type ◽  
Stereotactic Aspiration ◽  
Cystic Component ◽  
The Mean ◽  
Fine Print

Object. The goal of this study was to elucidate the role of gamma knife radiosurgery (GKS) and adjuvant stereotactic procedures by assessing the outcome of 31 consecutive patients harboring craniopharyngiomas treated between March 1993 and December 1999. Methods. There were 31 consecutive patients with craniopharyngiomas: 18 were men and 13 were women. The mean age was 32 years (range 3–69 years). The mean tumor volume was 9 cm3 (range 0.3–28 cm3). The prescription dose to the tumor margin varied from 9.5 to 16 Gy. The visual pathways received 8 Gy or less. Three patients underwent stereotactic aspiration to decompress the cystic component before GKS. The tumor response was classified by percentage reduction of tumor volume as calculated based on magnetic resonance imaging studies. Clinical outcome was evaluated according to improvement and dependence on replacement therapy. An initial postoperative volume increase with enlargement of a cystic component was found in three patients. They were treated by adjuvant stereotactic aspiration and/or Ommaya reservoir implantation. Tumor control was achieved in 87% of patients and 84% had fair to excellent clinical outcome in an average follow-up period of 36 months. Treatment failure due to uncontrolled tumor progression was seen in four patients at 26, 33, 49, and 55 months, respectively, after GKS. Only one patient was found to have a mildly restricted visual field; no additional endocrinological impairment or neurological deterioration could be attributed to the treatment. There was no treatment-related mortality. Conclusions. Multimodality management of patients with craniopharyngiomas seemed to provide a better quality of patient survival and greater long-term tumor control. It is suggested that GKS accompanied by adjuvant stereotactic procedures should be used as an alternative in treating recurrent or residual craniopharyngiomas if further microsurgical excision cannot promise a cure.

Gamma knife radiosurgery for uveal melanomas: an 8-year experience

2000 ◽  
Vol 93 (supplement_3) ◽  
pp. 184-188 ◽  
Author(s):  
Gerald Langmann ◽  
Gerhard Pendl ◽  
Georg Papaefthymiou ◽  
Helmuth Guss ◽  
Keyword(s):  
Gamma Knife ◽  
Ciliary Body ◽  
Tumor Regression ◽  
Gamma Knife Radiosurgery ◽  
Neovascular Glaucoma ◽  
Content Type ◽  
Prescription Dose ◽  
The Mean ◽  
Fine Print ◽  
Uveal Melanomas

Object. The authors report their experience using gamma knife radiosurgery (GKS) to treat uveal melanomas. Methods. Between 1992 and 1998, 60 patients were treated with GKS at a prescription dose between 45 Gy and 80 Gy. The mean diameter of the tumor base was 12.2 mm (range 3–22 mm). The mean height of the tumor prominence was 6.7 mm (range 3–12 mm). The eye was immobilized. The follow-up period ranged from 16 to 94 months. Tumor regression was achieved in 56 (93%) of 60 patients. There were four recurrences followed by enucleation. The severe side effect of neovascular glaucoma developed in 21 (35%) patients in a high-dose group with larger tumors and in proximity to the ciliary body. A reduction in the prescription dose to 40 Gy or less and excluding treatment to tumors near the ciliary body decreased the rate of glaucoma without affecting the rate of tumor control. Conclusions. Gamma knife radiosurgery at a prescription dose of 45 Gy or more can achieve tumor regression in 85% of the uveal melanomas treated. Neovascular glaucoma can develop in patients when using this dose in tumors near the ciliary body. It is advised that such tumors be avoided and that the prescription dose be reduced to 40 Gy.

P14.67 Long-term results of gamma knife radiosurgery for treatment of intracranial glomus jugulare tumors

2021 ◽  
Vol 23 (Supplement_2) ◽  
pp. ii50-ii51
Author(s):  
R M Emad Eldin ◽  
K M Abdel Karim ◽  
A M N El-Shehaby ◽  
W A Reda ◽  
A M Nabeel ◽  
...  
Keyword(s):  
Clinical Improvement ◽  
Gamma Knife ◽  
Tumor Volume ◽  
Gamma Knife Radiosurgery ◽  
Long Term Results ◽  
Glomus Jugulare ◽  
The Mean ◽  
Mean Time

Abstract BACKGROUND Glomus Jugulare tumors are benign but locally aggressive ones that represent a therapeutic challenge. Previous studies about the use of Gamma Knife Radiosurgery (GRS) in those tumors have documented good results that needed larger number of patients and longer follow up periods to be confirmed. MATERIAL AND METHODS Between August 2001 and December 2017, 70 patients with glomus jugulare tumors were treated at the Gamma Knife Center, Cairo. They were 46 females and 24 males. The mean age was 48 years (16–71 years). Nineteen of these patients were previously operated, 5 were partially embolized, 3 underwent embolization and subsequent surgery and 43 had gamma knife as their primary treatment. Volume-staged gamma knife radiosurgery was used in 10 patients and single-session in 60 patients, with a total of 86 sessions. The mean target volume was 12.7 cm3 (range 0.2 to 34.5 cm3). The mean tumor volume was 15.5 cm3 (range 0.2 to 105 cm3). The mean prescription dose was 14.5 Gy (range 12 to 18 Gy). RESULTS The mean follow up period was 60 months (range 18 to 206 months), and by the time of the data analysis, two of the patients were dead (66 and 24 months after GK treatment). The tumor control was 98.6% (69/70). Thirty-two tumors became smaller and 37 were unchanged. The symptoms improved in 36 patients, were stable in 32 patients, and worsened in 2 patients who developed a transient facial palsy and worsened hearing. Symptomatic improvement began before any reduction in tumor volume could be detected, where the mean time to clinical improvement was 7 months whereas the mean time to tumor shrinkage was 18 months. CONCLUSION This study about the long term follow up of the GKR for the intracranial glomus jugulare tumors confirmed that this is a highly effective and safe treatment. This data shows that the clinical improvement is not correlated with the radiological volume reduction.

scholarly journals P03.08 Large cerebral arteriovenous malformations management with Volume-staged gamma knife radiosurgery

2019 ◽  
Vol 21 (Supplement_3) ◽  
pp. iii26-iii26
Author(s):  
R M Emad Eldin ◽  
W A Reda ◽  
A M El-Shehaby ◽  
K Abdel Karim ◽  
A Nabeel ◽  
...  
Keyword(s):  
Gamma Knife ◽  
Arteriovenous Malformations ◽  
Gamma Knife Radiosurgery ◽  
Cerebral Arteriovenous Malformations ◽  
Factors Affecting ◽  
Prescription Dose ◽  
The Mean ◽  
Cerebral Avms ◽  
Grade 3

Abstract BACKGROUND Large cerebral arteriovenous malformations (AVM) pose a management dilemma because of the limited success of any single treatment modality by itself. Surgery alone is associated with significant morbidity and mortality. Similarly, embolization alone has limited efficacy. Volume-staged gamma knife radiosurgery (VSGR) has been developed for the treatment of large AVMs, to increase the efficacy and improve safety of treatment of these lesions. The aim of the study was to assess the efficacy and safety of VSGR technique for the treatment of large cerebral AVMs. METHODS The study included patients treated by VSGR between May 2009 and July 2015. All cases had large AVMs (>10 cc). These were 29 patients. RESULTS Twenty-four patients completed radiographic follow up with 15 obliteration cases (62.5%). There was a total of 56 sessions performed. The mean AVM volume was 16 cc (10.1–29.3 cc). The mean prescription dose was 18 Gy (14–22 Gy). The mean follow up duration was 43 months (21–73 months). One patient died during follow up from unrelated cause. Two cases suffered haemorrhage during follow up. Symptomatic edema developed in 5 (17%) patients. The factors affecting obliteration were smaller total volume, higher dose/stage, non-deep location, compact AVM, AVM score less than 3, >18 Gy dose and <15 cc total volume. The factors affecting symptomatic edema were smaller total volume and shorter time between first and last sessions (p 0.012). T2 image changes were affected by SM grade 3 or more (p 0.013) and AVM score 3 or more (p 0.014). CONCLUSION VSGR provides an effective and safe treatment option for large cerebral AVMs. Smaller AVM volume is associated with higher obliteration rate.

Long-term outcomes of Gamma Knife radiosurgery in patients with vestibular schwannomas

2011 ◽  
Vol 114 (2) ◽  
pp. 432-440 ◽  
Author(s):  
Erin S. Murphy ◽  
Gene H. Barnett ◽  
Michael A. Vogelbaum ◽  
Gennady Neyman ◽  
Glen H. J. Stevens ◽  
...  
Keyword(s):  
Gamma Knife ◽  
Gamma Knife Radiosurgery ◽  
Vestibular Schwannomas ◽  
Tumor Control ◽  
Tumor Diameter ◽  
Long Term Effects ◽  
Median Dose ◽  
The Mean

Object The authors sought to determine the long-term tumor control and side effects of Gamma Knife radiosurgery (GKRS) in patients with vestibular schwannomas (VS). Methods One hundred seventeen patients with VS underwent GKRS between January 1997 and February 2003. At the time of analysis, at least 5 years had passed since GKRS in all patients. The mean patient age was 60.9 years. The mean maximal tumor diameter was 1.77 ± 0.71 cm. The mean tumor volume was 1.95 ± 2.42 ml. Eighty-two percent of lesions received 1300 cGy and 14% received 1200 cGy. The median dose homogeneity ratio was 1.97 and the median dose conformality ratio was 1.78. Follow-up included MR imaging or CT scanning approximately every 6–12 months. Rates of progression to surgery were calculated using the Kaplan-Meier method. Results Of the 117 patients in whom data were analyzed, 103 had follow-up MR or CT images and 14 patients were lost to follow-up. Fifty-three percent of patients had stable tumors and 37.9% had a radiographically documented response. Imaging-documented tumor progression was present in 8 patients (7.8%), but in 3 of these the lesion eventually stabilized. Only 5 patients required a neurosurgical intervention. The estimated 1-, 3-, and 5-year rates of progression to surgery were 1, 4.6, and 8.9%, respectively. One patient (1%) developed trigeminal neuropathy, 4 patients (5%) developed permanent facial neuropathy, 3 patients (4%) reported vertigo, and 7 patients (18%) had new gait imbalance following GKRS. Conclusions Gamma Knife radiosurgery results in excellent local control rates with minimal toxicity for patients with VS. The authors recommend standardized follow-up to gain a better understanding of the long-term effects of GKRS.

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