Single-session Gamma Knife Radiosurgery Research Articles

Minimum cochlear dose impacts hearing after radiosurgery for sporadic vestibular schwannoma.

It is uncertain which cochlear dose parameters significantly impact hearing after stereotactic radiosurgery (SRS) for sporadic vestibular schwannoma (VS). The objective of this study was to determine the impact of cochlear dose parameters on hearing outcomes for patients with serviceable hearing (SH). This was a historical cohort study performed at a single tertiary center that included patients with sporadic VS and SH who underwent single-session Gamma Knife radiosurgery treatment from 2007 to 2022. Associations of cochlear dose parameters with time to non-SH and rates of change in pure-tone average (PTA) and word recognition score (WRS) following SRS were assessed. A total of 205 patients with SH underwent SRS for a sporadic VS. At SRS, 54 (26%) tumors were confined to the internal auditory canal and 151 (74%) extended into the cerebellopontine angle. At 2, 5, and 10 years following SRS, 62%, 37%, and 15% of patients maintained SH, respectively. The median time to non-SH was 1.8 years. The median rates of change in PTA and WRS were 6.0 dB of hearing loss per year and -6.5% per year, respectively. In a multivariable analysis, each 1-Gy increase in minimum cochlear dose was significantly associated with time to non-SH (HR 1.5, 95% CI 1.2-1.9), rate of change in PTA decibel hearing loss per year (parameter estimate [PE] 3.4, 95% CI 0.6-6.2), and rate of change in WRS percentage per year (PE -6.4, 95% CI -11.2 to -1.5). The associations of each 1-Gy increase in mean cochlear dose with hearing outcomes were only significant among patients with class B hearing (time to non-SH HR 1.3, 95% CI 1.1-1.6; rate of change in PTA PE 3.6, 95% CI 1.2-5.9; and rate of change in WRS PE -5.7, 95% CI -9.7 to -1.7). The minimum cochlear dose impacts hearing outcomes after SRS for VS and should be considered in radiosurgical treatment planning. In this cohort, the mean cochlear dose was only associated with hearing outcomes in the subgroup of patients with class B hearing at SRS.

Clinical and Radiological Response Following Single-Session Gamma Knife Radiosurgery in Cavernous Sinus Hemangiomas

Abstract Purpose Cavernous sinus hemangiomas (CSH) represent 2 to 3% of lesions occupying the cavernous sinus. The optimal management strategy for CSH is not established, with microsurgical resection and radiosurgery employed alone or in combination. Therefore, we aimed to analyze the efficacy and safety of gamma knife radiosurgery (GKRS) for CSH in a cohort of primary and residual CSH. Methods A retrospective analysis of 33 patients (26 primary and 7 residual CSH) that underwent single-session GKRS between 2012 and 2021 for CSH was performed. Demographic, clinical, radiological, and follow-up data were acquired, and clinicoradiological response following GKRS was assessed. Results The mean age of the cohort was 43 ± 13.5 years (range, 10–77). There were 9 males (27.3%) and 24 females (72.7%). The median lesion volume was 6.9 cc, ranging from 1.46 to 19.06 cc. The mean dose administered to the tumor margin was 13.50 ± 1.5 Gy (range, 12 to 15 Gy). The median duration of clinical follow-up was 41 months, over which period the mean reduction in tumor volume was 87.6%. Complete response, defined as absence of tumor on follow-up imaging, occurred in 23 patients (69.7%). Twenty-three patients (69.7%) showed clinical improvement following GKRS. There were no radiation-induced complications. Conclusion CSH have a distinct radiological appearance and a predictable response to radiosurgery. When used primarily in radiologically diagnosed CSH and as adjunctive therapy supplementing a subtotal excision, GKRS produces a high rate of volume reduction with the improvement of neurological function and minimal cranial nerve morbidity. Therefore, GKRS presents a viable alternative to surgery without the morbidity associated with surgical resection.

Long-term results of upfront, single-session Gamma Knife radiosurgery for large cystic vestibular schwannomas.

Anecdotally, cystic vestibular schwannomas (cVSs) are regarded to have unpredictable biologic activity with poorer clinical results, and most studies showed a less favorable prognosis following surgery. While stereotactic radiosurgery (SRS) is a well-established therapeutic option for small- to medium-sized VSs, cVSs are often larger, thus making upfront SRS more complicated. The purpose of this retrospective study was to assess the efficacy and safety of upfront SRS for large cVSs. The authors reviewed the data of 54 patients who received upfront, single-session Gamma Knife radiosurgery (GKRS) with a diagnosis of large cVS (> 4 cm3). Patients with neurofibromatosis type 2, multiple VSs, or recurrent VSs and < 24months of clinical and neuroimaging follow-up were excluded. Hearing loss (48.1%) was the primary presenting symptom. The majority of cVSs were Koos grade IV (66.7%), and the most prevalent cyst pattern was "mixed pattern of small and big cysts" (46.3%). The median time between diagnosis and GKRS was 12months (range, 1-147months). At GKRS, the median cVS volume was 6.95 cm3 (range, 4.1-22 cm3). The median marginal dose was 12Gy (range, 10-12Gy). The mean radiological and clinical follow-up periods were 62.2 ± 34.04months (range, 24-169months) and 94.9 ± 45.41months (range, 24-175months), respectively. At 2, 6, and 12years, the tumor control rates were 100%, 95.7%, and 85.0%, respectively. Tumor shrinkage occurred in 92.6% of patients (n = 50), tumor volume remained stable in 5.6% of patients (n = 3), and tumor growth occurred in 1.9% of patients (n = 1). At a median follow-up of 53.5months, the pre-GKRS tumor volume significantly decreased to 2.35 cm3 (p < 0.001). While Koos grade 3 patients had a greater possibility of attaining higher volume reduction, "multiple small thick-walled cyst pattern" and smaller tumor volumes decreased the likelihood of achieving higher volume reduction. Serviceable hearing (Gardner-Robertson Scale I-II) was present in 16.7% of patients prior to GKRS and it was preserved in all of these patients following GKRS. After GKRS, 1.9% of patients (n = 1) had new-onset trigeminal neuralgia. There was no new-onset facial palsy, hemifacial spasm, or hydrocephalus. Contrary to what was believed, our findings suggest that upfront GKRS seems to be a safe and effective treatment option for large cVSs.

Volume prediction for large brain metastases after hypofractionated gamma knife radiosurgery through artificial neural network.

The effectiveness of single-session gamma knife radiosurgery (GKRS) for small metastatic brain tumors has been proven, but hypofractionated GKRS (hfGKRS) for large brain metastases (BM) from the linear quadratic (LQ) model is uncertain. The purpose of this study was to investigate volume changes large BM after hfGKRS from the LQ model and predict volume changes using artificial neural network (ANN). We retrospectively investigated the clinical findings of 28 patients who underwent hfGKRS with large BM (diameter >3 cm or volume >10 cc). A total of 44 tumors were extracted from 28 patients with features. We randomly divided 30 large brain tumors as training set and 14 large brain tumors as test set. To predict the volume changes after hfGKRS, we used ANN models (single-layer perceptron (SLP) and multi-layer perceptron (MLP)). The volume reduction was 96% after hfGKRS for large BM from the LQ model. ANN model predicted volume changes with 70% and 80% accuracy for SLP and MLP, respectively. Even in large BM, hfGKRS from the LQ model could be a good treatment option. Additionally, the MLP model could predict volume changes with 80% accuracy after hfGKRS for large BM.

Stereotactic radiosurgery for orbital cavernous hemangiomas.

The goal of this study was to assess the safety and efficacy of single-session Gamma Knife radiosurgery (GKRS) for orbital cavernous hemangiomas (OCHs). Patients who presented with an OCH between September 1999 and May 2022 and were treated with single-session GKRS were included in this single-center cohort study. There were 23 patients (7 males and 16 females) in this study. The median margin dose was 12 Gy (range 11-13 Gy). The median clinical and radiological follow-ups were 45 months (range 5-190 months) and 45 months (range 6-190 months), respectively. Nine (69.2%) of 13 patients with visual acuity impairment had improvement in best corrected visual acuity. Of the 8 patients with visual field defects, 5 patients (62.5%) had complete resolution. Tumor regression was observed in 22 patients (95.7%). The mean relative reduction in tumor volume was 82.6% ± 23.7%. The relative reductions in tumor volume were 33%, 49%, 72%, 84%, and 89% at 6, 12, 24, 36, and 48 months, respectively. Adverse effects of radiation were not observed. GKRS appears to be safe and efficacious for treating OCHs over long-term follow-up. The treatment is associated with a high rate of regression in OCHs and remarkable improvement in both visual acuity and visual field deficits.

Predictive Factors of Radiation-Induced Changes Following Single-Session Gamma Knife Radiosurgery for Arteriovenous Malformations.

We evaluated for possible predictors of radiation-induced changes (RICs) after gamma knife radiosurgery (GKRS) for arteriovenous malformations (AVMs). We identified the nidal component within AVMs to analyze the correlation between the volume of brain parenchyma within the 50% isodose line (IDL) and RICs. We retrospectively reviewed patients with AVMs who underwent a single-session of GKRS at our institution between 2007 and 2017 with at least a 2-year minimum follow-up. Follow-up magnetic resonance images were evaluated for newly developed T2 signal changes and the proportions of nidus and intervening parenchyma were quantified. A total of 180 AVM patients (98 males and 82 females) with a median age of 34 years were included in the present study. The overall obliteration rate was 67.8%. The median target volume was 3.65 cc. The median nidus and parenchyma volumes within the 50% IDL were 1.54 cc and 2.41 cc, respectively. RICs were identified in 79 of the 180 patients (43.9%). AVMs associated with previous hemorrhages showed a significant inverse correlation with RICs. In a multivariate analysis, RICs were associated with a higher proportion of brain parenchyma within the 50% IDL (hazard ratio (HR) 169.033; p < 0.001) and inversely correlated with the proportion of nidus volume within the 50% IDL (HR 0.006; p < 0.001). Our study identified that a greater proportion of brain tissue between the nidus within the 50% IDL was significantly correlated with RICs. Nidus angioarchitectural complexity and the absence of a prior hemorrhage were also associated with RICs. The identification of possible predictors of RICs could facilitate radiosurgical planning and treatment decisions as well as the planning of appropriate follow-up after GKRS; this could minimize the risk of RICs, which would be particularly beneficial for the treatment of incidentally found asymptomatic AVMs.

Radiosurgery for Trigeminal Neuralgia Secondary to Dolichoectatic Vessels: Case Series and Review of Literature.

Even for seasoned neurosurgeons who have mastered the microvascular decompression (MVD) techniques, trigeminal neuralgia (TGN) secondary to vertebrobasilar dolichoectatic vessels remains a challenge. Often, patient is either medically infirm or unwilling for invasive surgical interventions. Alternative treatment options including Gamma Knife radiosurgery (GKRS) are considered in such a situation with variable success. This study aimed to evaluate the role of GKRS in patients with trigeminal neuralgia with dolichoectatic vessels and severe cross compression. We prospectively managed three male patients of intractable TGN secondary to dolichoectatic vascular compression with single-session GKRS. The cisternal component of the trigeminal nerve was targeted with 90 Gy radiation at 100% isodose with a single 4-mm collimator. The patients were regularly evaluated on clinical parameters for pain relief (Barrow Neurological Institute (BNI) score), sensory complaints, and outcome. All patients had satisfactory pain control (BNI I–IIIa) at 3 months of interval only to get recurrent pain (BNI IV–V) after 6 months. The treatment was eventually considered a failure after 6-month duration and one patient needed MVD for pain control. Post-GKRS pain control remains inferior in patients with dolichoectasia compared with typical TGN. GKRS should be offered only as a salvage or rescue procedure and should not be used as an alternative treatment of MVD in patient population with dolichoectatic vessels.

Outcomes from treatment of asymptomatic skull base meningioma with stereotactic radiosurgery.

Optimal management of asymptomatic skull base meningiomas is controversial. We evaluated the safety and efficiency of Gamma Knife radiosurgery (GKRS) for the management of asymptomatic skull base meningiomas. This retrospective study involved patients managed with GKRS for asymptomatic, skull base meningiomas from 1997 to 2019. Patient clinico-radiologic data, tumor characteristics, and procedural details were analyzed. Favorable outcome was defined as lack of procedure-related mortality or permanent neurologic morbidity and radiologic evidence of tumor control. Tumor progression and regression were defined as an increase or decrease of > 20% in volume from baseline to the last neuroimaging study respectively. Tumor volumes within ± 20% of baseline volume were considered stable. Thirty-seven patients (30 women), median age 68 years old (range 42-83 months) were managed with a single-session GKRS for 40 asymptomatic, skull base meningiomas. At a median clinical follow-up of 58.5 months (range 14-150 months), no mortality associated with the procedure or the treated tumor was noted. Permanent neurologic morbidity was 2.75%. There was a statistically significant decrease in mean tumor volume (p < 0.001) from 4.04 cc (SD 3.09 cc) prior to radiosurgery to 2.73 cc (SD 2.24 cc) at last follow-up. Higher margin dose was associated with tumor regression at last follow-up (HR = 1.351; 95%CI [1.094-1.669]; p = 0.05). As compared to natural history studies, GKRS affords long-standing tumor control and neurologic preservation in the vast majority of patients treated for asymptomatic, skull base meningiomas. Further study is necessary to identify the optimal management of asymptomatic skull base meningiomas.

Stereotactic radiosurgery for orbital cavernous venous malformation: a single center's experience for 15 years.

Stereotactic radiosurgery such as Gamma Knife radiosurgery (GKRS) has been shown to have a good treatment effect for orbital cavernous venous malformation (CVM). However, radiation-induced retinopathy or optic neuropathy is a vision-threatening complication of orbital irradiation. Predicting the post-treatment visual outcome is critical. Clinical and radiological outcomes were investigated in 30 patients who underwent GKRS for orbital CVM between July 2005 and February 2020. Measurement of peripapillary retinal nerve fiber layer (pRNFL) thickness using optical coherence tomography (OCT) was obtained in 14 patients. The median clinical and radiological follow-up periods were 46.6 months (range, 15.9-105.8) and 27.5 months (range, 15.4-105.8), respectively. Twenty-eight patients underwent multisession (4 fractions) GKRS. The median cumulative marginal dose was 20 Gy (range, 16-24). Two patients underwent single-session GKRS. Marginal doses were 15 Gy and 10.5 Gy in each patient. The volume of CVM decreased in 29 (97%) patients. Visual acuity was improved in 6 (20%) patients and was stable in 22 (73%) patients. Visual field defect and exophthalmos were improved in all patients. Serial investigation of OCT showed no statistically significant difference in pRNFL thickness after GKRS. Patients with normal average pRNFL thickness showed better visual recovery than patients with thin average pRNFL thickness. GKRS is an effective and safe treatment option for orbital CVM. The pRNFL thickness before GKRS can be a prognostic indicator for visual recovery in orbital CVM after GKRS.

Gamma knife radiosurgery in patients with Cushing’s disease: Comparison of aggressive pituitary corticotroph tumor versus corticotroph adenoma

Aggressive pituitary corticotroph tumors causing Cushing’s disease are rare, and there is limited data about their clinical management. Here, we aimed to report our long-term experience with gamma knife radiosurgery (GKRS) as adjuvant treatment in patients with residual or recurrent pituitary corticotroph tumors. This retrospective study included 45 adult patients (M/F, 7/38; mean age, 40.2 ± 13.1 years) with residual tumor or recurrence after initially successful surgical resection. Single-session GKRS was performed in all patients. Tumors with a Ki-67 value higher than 3 % and radiologic invasion to surrounding tissues were classified as aggressive tumor group. Clinical, hormonal and radiological findings were compared between the aggressive (n = 10) and non-aggressive adenoma (n = 35) groups. Following GKRS, tumor volumes were significantly reduced in both groups. The mean time to hormonal remission in the non-aggressive group was significantly shorter than in the aggressive group (23.5 ± 6.3 vs 33.0 ± 5.0 month, respectively, p < 0.05). New-onset hypopituitarism was identified in only seven patients (15 %) after GKRS in the whole cohort. The present study introduces several essential findings about aggressive corticotroph tumors. First, aggressive behavior tends to occur more frequently in male subjects. Second, time to GKRS was significantly shorter in the aggressive group. Moreover, a tumor volume ≥2 cm3 may be associated with clinical aggressiveness in corticotroph tumors. In conclusion, we suggest that early adjuvant GKRS is an effective treatment option in aggressive pituitary corticotroph tumors.

Gamma Knife Radiosurgery Followed by Flow-Reductive Embolization for Ruptured Arteriovenous Malformation.

Background: Aggressive treatment to achieve complete obliteration of brain arteriovenous malformation (AVM) is necessary in patients with a recent history of hemorrhage. The major drawback of Gamma knife radiosurgery (GKRS) alone for AVM is risk of bleeding during the latent period until the AVM occludes. At our center, patients who present with ruptured AVMs are frequently offered GKRS followed by embolization. The goal of this study was to compare outcomes of embolization for patients who have previously undergone GKRS for ruptured AVMs. Methods: A database including 150 GKRS for ruptured AVMs between November 2008 and October 2017 was reviewed. The embolized group was selected by including AVMs with post-GKRS embolization. The non-embolized group was defined as AVMs treated by GKRS alone. Outcomes including obliteration rate, incidence of repeat hemorrhage, and delayed cyst formation were compared between two groups. The predictive factors related to AVM obliteration and complications were analyzed. Results: The study consisted of 81 patients in the non-embolized group and 17 patients in the embolized group. Statistically significant differences were detected between the two groups with respect to age, Pollock-Flickinger score, Spetzler-Martin (SM) grade, eloquence of adjacent brain, and presence of aneurysms. The embolized group included more AVMs with larger median nidus volume. The predictive factors for the obliteration of ruptured AVMs were nidus volume, SM grade, Virginia Radiosurgery AVM Scale (VRAS), and Pollock-Flickinger score and for the subsequent hemorrhage were marginal dose, nidus volume, SM grade, VRAS, and Pollock-Flickinger score. The obliteration rates and complication rates after GKRS between groups were not significantly different. However, this study demonstrated statistically significant difference in the cumulative incidence of obliteration in AVMs with SM grade III and IV (p = 0.037). Conclusion: Although the current study demonstrated similar results in patients who underwent GKRS with and without embolization, the embolized group included more AVMs with larger nidus volume, higher SM grade, Pollock-Flickinger score, and aneurysm, which have a lower chance of obliteration and a higher probability of repeat hemorrhage. GKRS followed by embolization appears to be a beneficial approach for the treatment of ruptured AVMs that are at risk for obliteration failure and repeat hemorrhage during the latency period after single-session GKRS alone. Further studies involving a larger number of cases and continuous follow-up are necessary to confirm our conclusions.

Outcomes of stereotactic radiosurgery for pilocytic astrocytoma: an international multiinstitutional study.

The current standard initial therapy for pilocytic astrocytoma is maximal safe resection. Radiation therapy is considered for residual, recurrent, or unresectable pilocytic astrocytomas. However, the optimal radiation strategy has not yet been established. Here, the authors describe the outcomes of stereotactic radiosurgery (SRS) for pilocytic astrocytoma in a large multiinstitutional cohort. An institutional review board-approved multiinstitutional database of patients treated with Gamma Knife radiosurgery (GKRS) between 1990 and 2016 was queried. Data were gathered from 9 participating International Radiosurgery Research Foundation (IRRF) centers. Patients with a histological diagnosis of pilocytic astrocytoma treated using a single session of GKRS and with at least 6 months of follow-up were included in the analysis. A total of 141 patients were analyzed in the study. The median patient age was 14 years (range 2-84 years) at the time of GKRS. The median follow-up was 67.3 months. Thirty-nine percent of patients underwent SRS as the initial therapy, whereas 61% underwent SRS as salvage treatment. The median tumor volume was 3.45 cm3. The tumor location was the brainstem in 30% of cases, with a nonbrainstem location in the remainder. Five- and 10-year overall survival rates at the last follow-up were 95.7% and 92.5%, respectively. Five- and 10-year progression-free survival (PFS) rates were 74.0% and 69.7%, respectively. On univariate analysis, an age < 18 years, tumor volumes < 4.5 cm3, and no prior radiotherapy or chemotherapy were identified as positive prognostic factors for improved PFS. On multivariate analysis, only prior radiotherapy was significant for worse PFS. This represents the largest study of single-session GKRS for pilocytic astrocytoma to date. Favorable long-term PFS and overall survival were observed with GKRS. Further prospective studies should be performed to evaluate appropriate radiosurgery dosing, timing, and sequencing of treatment along with their impact on toxicity and the quality of life of patients with pilocytic astrocytoma.

RADI-33. DISTRIBUTED FRAMELESS GAMMA KNIFE RADIOSURGERY: A NEW TREATMENT PARADIGM FOR PATIENTS WITH BRAIN METASTASES

INTRODUCTION: Stereotactic radiosurgery (SRS) has excellent efficacy for patients with limited intracranial disease. Its use in patients with >10 brain metastases remains controversial. Nonetheless, cancer patients are living longer due to advancements in systemic therapeutics and avoiding the neurocognitive toxicities of whole brain radiation therapy is critical. Recent reports suggest that SRS may be effective in patients with ≥10 metastases. Treating large numbers of brain metastases in a single Gamma Knife radiosurgery (GKRS) treatment session poses several challenges. Treatment of metastases in close proximity to one another leads to an increased dose to normal brain, potentially increasing the risk of necrosis. Furthermore, single session treatment of multiple metastases may last several hours, causing significant patient discomfort. Here, we describe a novel treatment paradigm to address these issues: distributed frameless GKRS. Patients with ≥6 brain metastases undergo multi-session frameless GKRS with both temporal and spatial distribution over 2–5 sessions, decreasing treatment time per day and not treating adjacent metastases simultaneously. METHODS: We evaluated all patients with brain metastases who underwent distributed frameless SRS, using the Gamma Knife ICON, between January 2017 and November 2018. Fifty-one patients with 1097 unique lesions were included in this analysis. RESULTS: Mean patient age was 58.8 (range 29–89) years. Median follow-up was 4.1 (range: 0–20.4) months. The median number of metastases treated was 5 (range: 1–19) per treatment session and 11.5 (range: 3–82) per treatment course. The median number of treatment sessions per treatment course was 3 (range: 2–10). The median number of treatment courses, per patient, was 1 (range: 1–4). The median margin dose was 15 Gy. The median overall survival was 5.9 (range: 0.2–20.9) months. CONCLUSIONS: Distributed frameless Gamma Knife radiosurgery is technically feasible and should be considered in lieu of single session GKRS for patients with ≥6 brain metastases.

Hearing outcomes between multi-session and single-session radiosurgery for vestibular schwannoma: a single center study

Background: Hearing preservation rate after Gamma Knife radiosurgery (GKRS) for vestibular schwannoma (VS) remains low. The aim of this study was to study hearing outcomes between multisession and single session GKRS in patients with VS and determine prognostic factors associated with hearing preservation. Methods: A retrospective analysis of 561 consecutive patients with VS subjected to multisession (74 patients) or single session (487 patients) GKRS (from June 2011 to April 2015) was performed. Propensity score matching (PSM) based on patient age, gender, tumor volume and pre-GKRS hearing was used to compare the two groups. The tumor control rate and complications were evaluated, especially hearing preservation and its prognostic factors. Results: According to PSM, 29 patients from each group with similar characteristics were selected for the study. Patients’ age, tumor volume, pre-GKRS pure tone average (PTA) and radiographic follow-up period were not significantly different between the two groups (P>0.05). The tumor control rate was 75.9% for the multisession group compared with 62.1% for the single session group (P=0.1142); 20 patients had a less than 20 dB change in PTA in multisession group, with the hearing preservation rate of 69.0% (20/29) compared with 65.5% (19/29) in single session group (P=0.08). Multivariate analysis revealed that linear internal auditory canal (IAC) length was the only significant predictor of hearing loss in the multisession group. At last follow-up, one patient complaining of sudden hearing loss was diagnosed with tumor bleeding 12 months after multisession GKRS. One patient from multisession group and two patients from single session group suffered from temporal facial numbness. Facial spasm developed in one patient after multisession GKRS. Conclusions: Our results supported that multisession GKRS could be an effective and safe treatment option for VS compared to single session GKRS. The hearing preservation rate after multisession GKRS was not superior to single session radiosurgery in our short-term follow-up study. However, patients with longer IAC length may benefit from multisession strategy in terms of hearing preservation.

Tailored Treatment Options for Patients with Brain Metastases by a Relocatable Frame System with Gamma Knife Radiosurgery

To report on our experience with the Elekta Extend system, a relocatable frame system used in patients with brain metastases for single-session, hypofractionated, or staged hypofractionated Gamma Knife radiosurgery (GKRS); and the evaluation of its efficacy. From March 2014 to September 2016, 856 patients with brain metastases underwent GKRS at our hospital. Of them, 35 patients who were retrospectively investigated, were selected for treatment with GKRS using the relocatable frame system. Individualized treatment strategy was chosen according to prior treatment history, number, size and location of tumor, or tumor harboring gene mutation. Thirty-two (91.4%) patients underwent treatment with hypofractionated GKRS or staged hypofractionated GKRS, whereas 3 (8.6%) patients underwent single session GKRS. The mean radial setup difference from the reference measurements was 0.50 ± 0.16 mm. The median follow-up time after GKRS with the Extend system was 12 months (range, 1-45 months). The median overall survival time was 12 months (95% confidence interval 6.43-17.57). On multivariable analysis, performance status and extracranial metastases were independently prognostic factors for overall survival. Radiation necrosis developed in 4 cases (11.4%) during the follow-up period (2 with common terminology criteria for adverse events grade 2 and 2 with its grade 3). The relocatable frame system can maintain submillimetric accuracy and provide tailored treatment option with reasonable tumor control and good survival benefits in selected patients with brain metastases. Especially, hypofractionated GKRS or staged hypofractionated GKRS with noninvasive frame is a safe and effective treatment option for large brain metastases or tumor adjacent to eloquent structures.

Single fraction and multisession Gamma Knife radiosurgery for craniopharyngioma.

The optimal management of residual or recurring craniopharyngioma is still a matter of debate even though adjuvant radiation therapy plays a crucial role. Aim of our study is to report the results of single fraction or multisession Gamma Knife radiosurgery (GKRS) in patients with craniopharyngioma. We included 50 consecutive patients treated from 1994 to 2016. All patients had at least one post GKRS magnetic resonance imaging reviewed at our center. Vital status of all patients was assessed at the end of 2016. There were 29 males (58.0%) and 21 females (42.0%). Mean age was 41.5 ± 2.8year. Single session GKRS was delivered in 29 patients (58.0%). The mean tumor volume was 2.15 ± 0.3cm3 and the mean prescription dose to the tumor margin was 14.3 ± 0.3Gy. During a mean follow-up of 74.6 ± 8.4months, seven patients (14.0%) had recurrence of disease. The 5- and 10-year recurrence-free survivals were 90.3% (95% CI, 81.0-99.6%) and 78.4% (95% CI, 59.9-96.9%), respectively. Multisession GKRS was not less effective than single fraction GKRS. Eighteen of the 28 patients (64.3%) had a tumor volume decrease of at least 10%. No serious side effects occurred after GKRS treatment, except for one case of mild visual worsening. GKRS was effective for controlling the growth of residual or recurrent craniopharyngioma. Serious side effects were uncommon. Multisession GKRS seems a very promising tool to allow performing GKRS even in patients with large residual or recurrent craniopharyngioma.

Optimal strategy of gamma knife radiosurgery for craniopharyngiomas.

To analyze the outcomes of gamma knife radiosurgery (GKS) for craniopharyngiomas and elucidate the optimal strategy. Between 1998 and 2016, 35 patients underwent GKS for the treatment of 40 recurrent or residual craniopharyngiomas. Among 40 GKSs, 22 procedures were single-session GKSs and 18 procedures were fractionated GKSs. In cases of single-session GKS, the median marginal dose was 15Gy (range 10-20Gy). In cases of fractionated GKS, the median marginal dose was 6Gy (range 5-7.5Gy) of three fractions. The radiation dose was calculated to the biologic equivalent dose (BED) using α/β ratios of 10 and 2. The location of the tumor, the distance between the optic nerve and tumor (> 10mm), BED 10 (> 35Gy), and BED2 (> 80Gy) were statistically significant with overall response rate (P = 0.008, 0.02, 0.03, and 0.002, respectively). There was a statistically significant difference in progression-free survival according to the distance between the optic nerve and tumor (> 10mm) and the location of tumor (P = 0.03 and 0.03, respectively). Multivariate logistic regression analysis showed the hypothalamus group had an odds ratio of 0.04 compared with the suprasellar group for tumor progression. The group with BED2 > 80Gy had an odds ratio of 0.049 compared with the group with BED2 < 80Gy. A sufficient dose is required for treating craniopharyngiomas using single-session and fractionated GKS. The outcomes of GKS can be predicted according to the location of tumor, the distance between the optic nerve and tumor and BED value.

Is Fractionated Gamma Knife Radiosurgery a Safe and Effective Treatment Approach for Large-Volume (>10 cm3) Intracranial Meningiomas?

Even with great advances in surgery and improved clinical outcome, morbidity and mortality are still high for large-volume intracranial meningiomas (MNGs). Recently, Gamma Knife radiosurgery (GKS) has proven to be a safe and effective treatment for many patients with intracranial MNGs. However, single-session GKS may increase the risk of radiation-induced toxicity for large MNGs. Recently, fractionated GKS (FGKS) has been performed for an increasing number of patients with surgically high-risk and large intracranial tumors. In this study, we report our results on the efficacy and safety of FGKS for large MNGs. The authors performed a retrospective review of 70 patients who underwent GKS for large-volume (>10 cm3) intracranial MNGs between 2004 and 2015, with a minimum follow-up of 12 months. The authors classified these patients into 2 groups of single-session GKS, FGKS. The patients were followed by clinical examination and serial imaging with magnetic resonance imaging. In the single-session GKS group (42 patients), the median tumor volume was 15.2 cm3 (range 10.3-48.3 cm3); the median prescription dose was 12 Gy (range 8-14 Gy), and the median follow-up duration was 57.8 months (range 14.5-128.4 months). In the FGKS group (28 patients), the median tumor volume was 21 cm3 (range 10.2-54.7 cm3), and the median prescription was 7.5 Gy in 2 fractions (range 5-8 Gy), 6 Gy in 3 fractions (range 5-6.5 Gy), and 4.5 Gy in 4 fractions. The median follow-up duration for the FGKS group was 50 months (range 12.5-90.6 months). The overall 5-year tumor control rate was 92.9% in the FGKS group and 88.1% in the single-session GKS group. Fourteen (33.3%) symptomatic complications after single-session GKS were noted, including 5 cases of hemiparesis, 4 of seizure, 3 of peritumoral edema, and 2 of hydrocephalus. Two (7.1%) symptomatic complications after FGKS were noted, including 2 cases of hemiparesis. The FGKS group had higher progression-free survival (PFS) rate at 5 years (92.9% vs. 88.1%), but the differences did not reach statistical significance (P= 0.389). The patients in the FGKS group, however, experienced a lower complication rate compared with patients with a single-session GKS group (P= 0.017, hazard ratio, 5.7:1). When the large-volume (>10 cm3) intracranial MNGs are expected to have high morbidity after microsurgery and for patients that have a poor medical status for surgery, FGKS can be considered an alternative with good tumor control and lower complications rates compared with single-session GKS (P= 0.017).

Single-session Gamma Knife radiosurgery for optic pathway/hypothalamic gliomas

OBJECTIVE Because of their critical and central location, it is deemed necessary to fractionate when considering irradiating optic pathway/hypothalamic gliomas. Stereotactic fractionated radiotherapy is considered safer when dealing with gliomas in this location. In this study, the safety and efficacy of single-session stereotactic radiosurgery for optic pathway/hypothalamic gliomas were reviewed. METHODS Between December 2004 and June 2014, 22 patients with optic pathway/hypothalamic gliomas were treated by single-session Gamma Knife radiosurgery. Twenty patients were available for follow-up for a minimum of 1 year after treatment. The patients were 5 to 43 years (median 16 years) of age. The tumor volume was 0.15 to 18.2 cm3 (median 3.1 cm3). The prescription dose ranged from 8 to 14 Gy (median 11.5 Gy). RESULTS The mean follow-up period was 43 months. Five tumors involved the optic nerve only, and 15 tumors involved the chiasm/hypothalamus. Two patients died during the follow-up period. The tumors shrank in 12 cases, remained stable in 6 cases, and progressed in 2 cases, thereby making the tumor control rate 90%. Vision remained stable in 12 cases, improved in 6 cases, and worsened in 2 cases in which there was tumor progression. Progression-free survival was 83% at 3 years. CONCLUSIONS The initial results indicate that single-session Gamma Knife radiosurgery is a safe and effective treatment option for optic pathway/hypothalamic gliomas.

PC3 - 141 Long-Term Results of Stereotactic Radiosurgery for Skull Base Meningiomas

Gamma knife radiosurgery (GKRS) is well-established in the management of inaccessible, recurrent, or residual benign skull base meningiomas. Most series report clinical outcome parameters and complications in the short -intermediate period after radiosurgery. Reports of long-term tumor control and neurological status are still lacking. Objective: We report the presentation, treatment, and long-term outcome of skull base meningiomas after GKRS. Methods: From a prospectively collected IRB approved database, we selected patients with a WHO grade I skull base meningioma treated with a single-session GKRS and a minimum of 60 months follow up. 135 patients, 54.1% males (n=73) form the cohort. Median age was 54 years (19-80). Median tumor volume was 4.7 cm3 (0.5-23). Median margin dose was 15 Gy (7.5-36). Median follow up was 102.5 months (60.1-235.4). Patient and tumor characteristics were assessed to determine predictors of neurological function and tumor progression. Results: At last follow up, tumor volume control was achieved in 88.1% (n=119). Post-GKRS clinical improvement or stability was reported in 61.5%. The 5, 10, and 15 years actuarial progression free survival rates are 100%, 95.4%, and 68.8%, respectively. Favorable outcome (both tumor control and clinical preservation/improvement) was attained in 60.8% (n=79). Pre-GKRS performance status (KPS) was shown to influence tumor progression (p=0.0001) and post-GKRS clinical improvement / preservation (p=0.003). Conclusion: GKRS offers a highly durable rate of tumor control for WHO-I skull base meningiomas, with an acceptably low incidence of neurological deficits. KPS at the time of radiosurgery serves as a reliable long-term predictor of overall outcome.