RTHP-11. THE EFFECT OF PRESCRIPTION ISODOSE LINE ON LOCAL CONTROL AND RADIOGRAPHIC RESPONSE IN GAMMA KNIFE RADIOSURGERY OF VESTIBULAR SCHWANNOMA

Abstract Traditionally, the 50% isodose line (IDL) is used for prescription dose when vestibular schwannomas (VS) are treated with Gamma Knife radiosurgery (GKRS). To compare the effect of IDL on treatment outcomes, propensity score-matched analysis according to age at time of GKRS and tumor volume (TV) between cohorts treated at 40%IDL and 50%IDL was performed. Patients with no history of neurofibromatosis, GKRS prescribed marginal dose of 12–14 Gy and TV ≤ 10 cc were identified. Patients were excluded if follow-up time was < 2 years. Eventually, 30 and 28 patients were included in 40%IDL and 50%IDL cohorts, respectively. Mean age and TV were not significantly different between 40%IDL and 50%IDL groups; 54.5 versus 54.0 years (p=0.891) and 2148.61 versus 2031.10 mm3 (p=0.844), respectively. Median prescription dose was 12 Gy in both groups. At median follow-up times of 111 and 72 months, the 2, 5 and 10-year local control were 100%, 96.4% and 96.4% for 40%IDL and 96.4%, 86.7%, and 86.7% for 50%IDL (p=0.243), respectively. Among 40 patients with accessible follow-up MRIs (40%IDL-n=19, 50%IDL-n=21), volume reduction at last follow-up MRIs and rate of reduction per year for 40%IDL and 50%IDL were 48.1% versus 38.3% (p=0.05) and 5.5% versus 6% (p=0.749), respectively. Of 21 patients with serviceable hearing prior to GKRS and available audiograms after GKRS (40%IDL-n=8, 50%IDL-n=13), the 2, 5 and 10-year hearing preservation rate were 100%, 83.3% and 62.5% for 40%IDL versus 76.2%, 57.1% and 11.4% for 50%IDL (p=0.017). Facial paresthesia, facial palsy and ataxia/gait disturbance requiring steroid and/or shunt were lower in 40%IDL compared to the 50%IDL; 6.7% versus 17.9% (p=0.208) and 3.3% versus 7.1% (p=0.532). To summarize, VS treated at 40%IDL have slightly better local control, although not statistically significant, compared to tumors treated at 50%IDL. However, hearing preservation and safety seem to be more favorable toward 40%IDL group.

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Gamma Knife radiosurgery for vestibular schwannomas: evaluation of tumor control and its predictors in a large patient cohort in The Netherlands

Journal of Neurosurgery ◽

10.3171/2015.4.jns142415 ◽

2016 ◽

Vol 124 (6) ◽

pp. 1619-1626 ◽

Cited By ~ 41

Author(s):

Stijn Klijn ◽

Jeroen B. Verheul ◽

Guus N. Beute ◽

Sieger Leenstra ◽

Jef J. S. Mulder ◽

...

Keyword(s):

Gamma Knife ◽

Tumor Volume ◽

Gamma Knife Radiosurgery ◽

Hearing Preservation ◽

Cox Proportional Hazards Model ◽

Tumor Control ◽

Complication Rates ◽

Tumor Control Rate ◽

Large Patient

OBJECT The authors of this study sought to assess tumor control and complication rates in a large cohort of patients who underwent Gamma Knife radiosurgery (GKRS) for vestibular schwannoma (VS) and to identify predictors of tumor control. METHODS The records of 420 patients treated with GKRS for VS with a median marginal dose of 11 Gy were retrospectively analyzed. Patients with neurofibromatosis Type 2 or who had undergone treatment for VS previously were excluded. The authors assessed tumor control and complication rates with chart review and used the Cox proportional hazards model to identify predictors of tumor control. Preservation of serviceable hearing, defined as Gardner-Robertson Class I–II, was evaluated in a subgroup of 71 patients with serviceable hearing at baseline and with available follow-up audiograms. RESULTS The median VS tumor volume was 1.4 cm3, and the median length of follow-up was 5.1 years. Actuarial 5-and 10-year tumor control rates were 91.3% and 84.8%, respectively. Only tumor volume was a statistically significant predictor of tumor control rate. The tumor control rate decreased from 94.1% for tumors smaller than 0.5 cm3 to 80.7% for tumors larger than 6 cm3. Thirteen patients (3.1%) had new or increased permanent trigeminal nerve neuropathy, 4 (1.0%) had new or increased permanent facial weakness, and 5 (1.2%) exhibited new or increased hydrocephalus requiring a shunting procedure. Actuarial 3-year and 5-year hearing preservation rates were 65% and 42%, respectively. CONCLUSIONS The 5-year actuarial tumor control rate of 91.3% in this cohort of patients with VS compared slightly unfavorably with the rates reported in other large studies, but the complication and hearing preservation rates in this study were similar to those reported previously. Various factors may contribute to the observed differences in reported outcomes. These factors include variations in treatment indication and in the definition of treatment failure, as well as a lack of standardization of terminology and of evaluation of complications. Last, differences in dosimetric variables may also be an explanatory factor.

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Hearing preservation after Gamma Knife radiosurgery for cerebellopontine angle meningiomas

Journal of Neurosurgery ◽

10.3171/2018.7.gks181308 ◽

2018 ◽

Vol 129 (Suppl1) ◽

pp. 38-46 ◽

Cited By ~ 1

Author(s):

Amr M. N. El-Shehaby ◽

Wael A. Reda ◽

Khaled M. Abdel Karim ◽

Ahmed M. Nabeel ◽

Reem M. Emad Eldin ◽

...

Keyword(s):

Gamma Knife ◽

Gamma Knife Radiosurgery ◽

Hearing Preservation ◽

Tumor Control ◽

Factors Affecting ◽

Hearing Outcome ◽

Group A ◽

Group B ◽

Preservation Rate

OBJECTIVEThe objective of this study was to assess hearing function after Gamma Knife treatment of cerebellopontine angle (CPA) meningiomas and assess factors affecting hearing outcome. Additionally, the authors opted to compare these results with those after Gamma Knife treatment of vestibular schwannomas (VSs), because most of the information on hearing outcome after stereotactic radiosurgery (SRS) comes from reports on VS treatment. Hearing preservation, to the best of the authors’ knowledge, has never been separately addressed in studies involving Gamma Knife radiosurgery (GKRS) for CPA meningiomas.METHODSThis study included all patients who underwent a single session of GKRS between 2002 and 2014. The patients were divided into two groups. Group A included 66 patients with CPA meningiomas with serviceable hearing and tumor extension into the region centered on the internal auditory meatus. Group B included 144 patients with VSs with serviceable hearing. All patients had serviceable hearing before treatment (Gardner-Robertson [GR] Grades I and II). The median prescription dose was 12 Gy (range 10–12 Gy) in both groups. The median follow-up of groups A and B was 42 months (range 6–149 months) and 49 months (range 6–149 months), respectively.RESULTSAt the last follow-up, the tumor control rate was 97% and 94% in groups A and B, respectively. Hearing preservation was defined as maintained serviceable hearing according to GR hearing score. The hearing preservation rate was 98% and 66% and the 7-year actuarial serviceable hearing preservation rate was 75% and 56%, respectively, between both groups. In group A, the median maximum cochlear dose in the patients with stable and worsened hearing grade was 6.3 Gy and 5.5 Gy, respectively. In group B, factors affecting hearing preservation were cochlear dose ≤ 7 Gy, follow-up duration, and tumor control. The only determinant of hearing preservation between both groups was tumor type.CONCLUSIONSGKRS for CPA meningiomas provides excellent hearing preservation in addition to high tumor control rate. Hearing outcome is better with CPA meningiomas than with VSs. Further long-term prospective studies on determinants of hearing outcome after GKRS for CPA meningiomas should be conducted.

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The Energy Index Does Not Affect Local Control of Brain Metastases Treated by Gamma Knife Stereotactic Radiosurgery

Neurosurgery ◽

10.1227/neu.0000000000000750 ◽

2015 ◽

Vol 77 (1) ◽

pp. 119-125 ◽

Cited By ~ 4

Author(s):

Ashish Jani ◽

Tzlil Rozenblat ◽

Andrew M. Yaeh ◽

Tavish Nanda ◽

Shumaila Saad ◽

...

Keyword(s):

Multivariate Analysis ◽

Brain Metastases ◽

Gamma Knife ◽

Local Control ◽

Tumor Volume ◽

Complete Response ◽

Local Failure ◽

Energy Index ◽

Prescription Dose

Abstract BACKGROUND: The energy index (EI) is a measure of dose homogeneity within a target volume calculated by the integral dose divided by the product of prescription dose and tumor volume. OBJECTIVE: To assess whether a higher EI is associated with greater local control for brain metastases (BMs) treated by Gamma Knife radiosurgery (GKRS). METHODS: We reviewed all patients treated with GKRS for BM at our institution between January 2009 and February 2014. Data on the prescription dose, prescription isodose line, minimum dose, mean dose, integral dose, tumor volume, and EI were collected. Tumor response was assessed by reviewing follow-up brain imaging studies and classified according to the Response Evaluation Criteria in Solid Tumors. Local control per lesion and dosimetric prognostic factors for local control were assessed by univariate and multivariate Cox proportional hazards regression analyses. RESULTS: Of 213 patients treated, 126 had follow-up imaging available with a median follow-up of 6 months. Three hundred seventy-three individual tumors were analyzed. Of these, 133 showed a complete response, 157 showed a partial response, 46 remained stable, and 37 developed local failure. Tumors with EI ≥1.6 mJ.mL−1.Gy−1 showed a higher rate of complete response. Local control rates at 6, 11, and 17 months were 95.4%, 86.5%, and 81.5%, respectively. On univariate analysis, the following factors were associated with higher rates of local failure: prescription doses of 16 and 18 Gy compared with a prescription dose of 20 Gy. The following factors were associated with a greater rate of local control: maximum dose and mean dose. On multivariate analysis, the only statistically significant factor associated with a greater rate of local failure was prescription dose of 16 Gy compared with 20 Gy. CONCLUSION: GKRS for BM results in a high rate of local control with an 11-month rate of 86.5%. A higher EI was not significantly associated with a higher rate of local control on multivariate analysis. Prescription dose was found to be the only significant predictor of local control on multivariate analysis.

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Gamma Knife radiosurgery for vestibular schwannoma: clinical results at long-term follow-up in a series of 379 patients

Journal of Neurosurgery ◽

10.3171/2014.8.gks141506 ◽

2014 ◽

Vol 121 (Suppl_2) ◽

pp. 123-142 ◽

Cited By ~ 55

Author(s):

Nicola Boari ◽

Michele Bailo ◽

Filippo Gagliardi ◽

Alberto Franzin ◽

Marco Gemma ◽

...

Keyword(s):

Gamma Knife ◽

Tumor Volume ◽

Gamma Knife Radiosurgery ◽

Hearing Preservation ◽

Class I ◽

Medium Size ◽

Tumor Control ◽

Long Term Follow Up

ObjectSince the 1990s, Gamma Knife radiosurgery (GKRS) has become the first-line treatment option for small- to medium-size vestibular schwannomas (VSs), especially in patients without mass effect–related symptoms and with functional hearing. The aim of this study was to assess the safety and efficacy of GKRS, in terms of tumor control, hearing preservation, and complications, in a series of 379 consecutive patients treated for VS.MethodsOf 523 patients treated at the authors' institution for VS between 2001 and 2010, the authors included 379 who underwent GKRS as the primary treatment. These patients were not affected by Type 2 neurofibromatosis and had clinical follow-up of at least 36 months. Clinical follow-up (mean and median 75.7 and 69.5 months, respectively) was performed for all patients, whereas audiometric and quantitative radiological follow-up examinations were obtained for only 153 and 219 patients, respectively. The patients' ages ranged from 23 to 85 years (mean 59 years). The mean tumor volume was 1.94 ± 2.2 cm3 (median 1.2 cm3, range 0.013–14.3 cm3), and the median margin dose was 13 Gy (range 11–15 Gy). Parameters considered as determinants of the clinical outcome were long-term tumor control, hearing preservation, and complications. A statistical analysis was performed to correlate clinical outcomes with the radiological features of the tumor, dose-planning parameters, and patient characteristics.ResultsControl of the tumor with GKRS was achieved in 97.1% of the patients. In 82.7% of the patients, the tumor volume had decreased at the last follow-up, with a mean relative reduction of 34.1%. The rate of complications was very low, with most consisting of a transient worsening of preexisting symptoms. Patients who had vertigo, balance disorders, or facial or trigeminal impairment usually experienced a complete or at least significant symptom relief after treatment. However, no significant improvement was observed in patients previously reporting tinnitus. The overall rate of preservation of functional hearing at the long-term follow-up was 49%; in patients with hearing classified as Gardner-Robertson (GR) Class I, this value was 71% and reached 93% among cases of GR Class I hearing in patients younger than 55 years.ConclusionsGamma Knife radiosurgery is a safe and effective treatment for VS, achieving tumor control in 97.1% of cases and resulting in a very low morbidity rate. Younger GR Class I patients had a significantly higher probability of retaining functional hearing even at the 10-year follow-up; for this reason, the time between symptom onset, diagnosis, and treatment should be shortened to achieve better outcomes in functional hearing preservation.

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

Neuro-Oncology ◽

10.1093/neuonc/noab180.175 ◽

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.

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

Neuro-Oncology ◽

10.1093/neuonc/noz126.089 ◽

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.

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Hearing preservation in patients with vestibular schwannoma treated with Gamma Knife surgery

Journal of Neurosurgery ◽

10.3171/2012.10.jns12880 ◽

2013 ◽

Vol 118 (3) ◽

pp. 571-578 ◽

Cited By ~ 40

Author(s):

Andrew M. Baschnagel ◽

Peter Y. Chen ◽

Dennis Bojrab ◽

Daniel Pieper ◽

Jack Kartush ◽

...

Keyword(s):

Hearing Loss ◽

Gamma Knife ◽

Vestibular Schwannoma ◽

Hearing Preservation ◽

Gamma Knife Surgery ◽

Speech Discrimination ◽

Before And After ◽

Nerve Dysfunction ◽

Preservation Rate

Object Hearing loss after Gamma Knife surgery (GKS) in patients with vestibular schwannoma has been associated with radiation dose to the cochlea. The purpose of this study was to evaluate serviceable hearing preservation in patients with VS who were treated with GKS and to determine if serviceable hearing loss can be correlated with the dose to the cochlea. Methods Forty patients with vestibular schwannoma with serviceable hearing were treated using GKS with a median marginal dose of 12.5 Gy (range 12.5–13 Gy) to the 50% isodose volume. Audiometry was performed prospectively before and after GKS at 1, 3, and 6 months, and then every 6 months thereafter. Hearing preservation was based on pure tone average (PTA) and speech discrimination (SD). Serviceable hearing was defined as PTA less than 50 dB and SD greater than 50%. Results The median cochlear maximum and mean doses were 6.9 Gy (range 1.6–16 Gy) and 2.7 Gy (range 0.7–5.0 Gy), respectively. With a median audiological follow-up of 35 months (range 6–58 months), the 1-, 2-, and 3-year actuarial rates of maintaining serviceable hearing were 93%, 77%, and 74%, respectively. No patient who received a mean cochlear dose less than 2 Gy experienced serviceable hearing loss (p = 0.035). Patients who received a mean cochlear dose less than 3 Gy had a 2-year hearing preservation rate of 91% compared with 59% in those who received a mean cochlear dose of 3 Gy or greater (p = 0.029). Those who had more than 25% of their cochlea receiving 3 Gy or greater had a higher rate of hearing loss (p = 0.030). There was no statistically significant correlation between serviceable hearing loss and age, tumor size, pre-GKS PTA, pre-GKS SD, pre-GKS Gardner-Robertson class, maximum cochlear dose, or the percentage of cochlear volume receiving 5 Gy. On multivariate analysis there was a trend toward significance for serviceable hearing loss with a mean cochlear dose of 3 Gy or greater (p = 0.074). Local control was 100% at 24 months. No patient developed facial or trigeminal nerve dysfunction. Conclusions With a median mean cochlear dose of 2.7 Gy, the majority of patients with serviceable hearing retained serviceable hearing 3 years after GKS. A mean cochlear dose less than 3 Gy was associated with higher serviceable hearing preservation.

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CYBERKNIFE RADIOSURGERY FOR TRIGEMINAL SCHWANNOMAS

Neurosurgery ◽

10.1227/01.neu.0000341629.57676.db ◽

2009 ◽

Vol 64 (suppl_2) ◽

pp. A14-A18 ◽

Cited By ~ 7

Author(s):

Gordon T. Sakamoto ◽

D. John Borchers ◽

Furen Xiao ◽

Hee-Jin Yang ◽

Steven D. Chang ◽

...

Keyword(s):

Surgical Resection ◽

Gamma Knife ◽

Tumor Volume ◽

Gamma Knife Radiosurgery ◽

Benign Tumors ◽

Tumor Control ◽

Modest Improvement ◽

Facial Numbness ◽

The Mean

Abstract OBJECTIVE Trigeminal schwannomas (TS) are benign tumors that are managed by surgical resection and/or stereotactic radiosurgery. Most radiosurgical series report results using the gamma knife. The CyberKnife (Accuray, Inc., Sunnyvale, CA) is a frameless, robotic stereotactic radiosurgical system. In this series, we report our experience using the CyberKnife in the treatment of TS. METHODS We retrospectively reviewed the medical records and diagnostic imaging in 13 consecutive patients with TS who were treated with the CyberKnife from 2003 to 2007. Seven patients had a previous surgical resection. The mean tumor volume was 6.3 mL (range, 0.39–19.98 mL), and the mean marginal dose was 18.5 Gy. Six of the tumors were treated in a single session. The mean clinical follow-up period was 21.8 months (range, 7–53 months). RESULTS In this series, the tumor control rate was 100%. The average reduction in tumor volume was 45% (range, 14–98%). A modest improvement in facial pain was noted in 4 of the 6 patients who presented with this symptom. One patient had improvement in facial numbness, and another had improvement in pretreatment headaches. One patient developed jaw weakness and facial dysesthesia, and another patient developed asymptomatic radiation necrosis. CONCLUSION Although the length of follow-up is limited, we report our initial experience with CyberKnife treatment of TS. Our results demonstrate tumor control rates and clinical outcomes that parallel those of previous reports using gamma knife radiosurgery; however, long-term follow-up studies are needed.

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Gamma Knife radiosurgery for treatment of growing vestibular schwannomas in patients with neurofibromatosis Type 2: a matched cohort study with sporadic vestibular schwannomas

Journal of Neurosurgery ◽

10.3171/2016.9.jns161463 ◽

2018 ◽

Vol 128 (1) ◽

pp. 49-59 ◽

Cited By ~ 11

Author(s):

Ivo J. Kruyt ◽

Jeroen B. Verheul ◽

Patrick E. J. Hanssens ◽

Henricus P. M. Kunst

Keyword(s):

Gamma Knife ◽

Tumor Volume ◽

Gamma Knife Radiosurgery ◽

Neurofibromatosis Type ◽

Hearing Preservation ◽

Vestibular Schwannomas ◽

Tumor Control ◽

Nerve Function

OBJECTIVENeurofibromatosis Type 2 (NF2) is a tumor syndrome characterized by an autosomal dominant pattern of inheritance. The hallmark of NF2 is the development of bilateral vestibular schwannomas (VSs), generally by 30 years of age. One of the first-line treatment options for small to medium-large VSs is radiosurgery. Although radiosurgery shows excellent results in sporadic VS, its use in NF2-related VS is still a topic of dispute. The aim of this study was to evaluate long-term tumor control, hearing preservation rates, and factors influencing outcome of optimally dosed, contemporary Gamma Knife radiosurgery (GKRS) for growing VSs in patients with NF2 and compare the findings to data obtained in patients with sporadic VS also treated by means of GKRS.METHODSThe authors performed a retrospective analysis of 47 growing VSs in 34 NF2 patients who underwent GKRS treatment performed with either the Model C or Perfexion Leksell Gamma Knife, with a median margin dose of 11 Gy. Actuarial tumor control rates were estimated using the Kaplan-Meier method. For patient- and treatment-related factors, a Cox proportional hazards model was used to identify predictors of outcome. Trigeminal, facial, and vestibulocochlear nerve function were assessed before and after treatment. NF2-related VS patients were matched 1:1 with sporadic VS patients who were treated in the same institute, and the same indications for treatment, definitions, and dosimetry were used in order to compare outcomes.RESULTSActuarial tumor control rates in NF2 patients after 1, 3, 5, and 8 years were 98%, 89%, 87%, and 87%, respectively. Phenotype and tumor volume had significant hazard rates of 0.086 and 22.99, respectively, showing that Feiling-Gardner phenotype and a tumor volume not exceeding 6 cm3 both were associated with significantly better outcome. Actuarial rates of serviceable hearing preservation after 1, 3, 5, and 7 years were 95%, 82%, 59%, and 33%, respectively. None of the patients experienced worsening of trigeminal nerve function. Facial nerve function worsened in 1 patient (2.5%). No significant differences in tumor control, hearing preservation, or complications were found in comparing the results of GKRS for NF2-related VS versus GKRS for sporadic VS.CONCLUSIONSWith modern GKRS, the use of low margin doses for treating growing VSs in patients with NF2 demonstrates good long-term tumor control rates. Feiling-Gardner phenotype and tumor volume smaller than 6 cm3 seem to be independently associated with prolonged progression-free survival, highlighting the clinical importance of phenotype assessment before GKRS treatment. In addition, no significant differences in tumor control rates or complications were found in the matched-control cohort analysis comparing GKRS for VS in patients with NF2 and GKRS for sporadic VS. These results show that GKRS is a valid treatment option for NF2-related VS, in addition to being a good option for sporadic VS, particularly in patients with the Feiling-Gardner phenotype and/or tumors that are small to medium in size. Larger tumors in patients with the Wishart phenotype appear to respond poorly to radiosurgery, and other treatment modalities should therefore be considered in such cases.

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RADI-05. FRACTIONATED TREATMENT OF BRAIN METASTASES WITH GAMMA KNIFE ICON

Neuro-Oncology Advances ◽

10.1093/noajnl/vdz014.098 ◽

2019 ◽

Vol 1 (Supplement_1) ◽

pp. i22-i22

Author(s):

Jameson Mendel ◽

Ankur Patel ◽

Toral Patel ◽

Robert Timmerman ◽

Tu Dan ◽

...

Keyword(s):

Brain Metastasis ◽

Brain Metastases ◽

Gamma Knife ◽

Local Control ◽

Stereotactic Radiotherapy ◽

Tumor Volume ◽

Univariate Analysis ◽

Local Failure ◽

Fractionated Stereotactic Radiotherapy

Abstract PURPOSE/OBJECTIVE(S): Stereotactic radiosurgery with Gamma Knife is a common treatment modality for patients with brain metastasis. The Gamma Knife ICON allows for immobilization with an aquaplast mask, permitting fractionated treatments. We describe one of the first experiences utilizing this technique with brain metastasis and evaluate outcomes. MATERIALS/METHODS: From June 2017 to November 2018, 29 patients with 43 separate intracranial lesions were treated with fractionated stereotactic radiotherapy using the gamma knife ICON at a single institution. Patients received between 20–30 Gy in 3–5 fractions with no margin over the course of 5 to 23 days. Local control was physician assessed. Local failure over time was modeled using cumulative incidence; lesions were censored at last radiographic follow up. RESULTS: Median tumor volume and prescription isodose was 7.7 cm3 (range 0.3–43.9) and 50% (range 40–65), respectively. Median radiographic follow-up was 7 months and median survival was 9 months. Radiation necrosis occurred in 3/3 patients treated with 27 Gy in 3 fractions, one requiring therapeutic resection. Incidence of local failure for all treated lesions was 9% at 1 year. Tumor volume >7 cm3 was associated with local failure on univariate analysis (p=0.025). 100% (2/2) lesions treated with 20 Gy in 5 fractions developed local recurrence. CONCLUSION: Fractionated stereotactic radiotherapy with the Gamma Knife ICON provides excellent local control for small and large brain metastases with minimal toxicity. Tumors >7 cm3 should receive at least 30 Gy in 5 fractions for optimal control. Treatment with 27 Gy in 3 fractions appears to have high rates of treatment related toxicity and should be avoided.

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