Gamma Knife surgery of large meningiomas: early response to treatment

Long-term outcomes following upfront single-session gamma knife stereotactic radiosurgery for large volume meningiomas

BACKGROUND

Stereotactic radiosurgery (SRS) for the management of small and medium-sized intracranial meningiomas is well defined. However, limited studies evaluating long-term outcomes following SRS for large-volume meningiomas (LVMs) exist. Here, we report a large single-institution experience in using upfront single-session SRS to manage LVMs.

METHODS

This retrospective review included 112 patients (83 female, 74%) managed with single-session SRS for LVMs (> 10 cc) between 1987 and 2022. Exclusion criteria consisted of prior meningioma surgical resection or follow-up < 2 years. Tumors were classified as supratentorial (35%) or skull-base (65%). The median tumor volume was 13 cc (range: 10-24.7), and the median margin dose was 12 Gy (range: 10-15). Overall, 101 (90%) patients were neurologically symptomatic at SRS.

RESULTS

The median follow-up was 106 months (range: 24-307). Sixteen (14%) LVMs demonstrated tumor progression at a median time of 43 months (range: 7-181) following SRS. Local tumor control (LTC) rates at 3-years, 5-years, and 10-years were 98% (95%CI: 91-99), 97% (95% CI: 94-100) and 88% (95% CI: 80-96), respectively. Tumor volume > 17 cc (HR: 3.26, 95% CI: 1.17-9.08, p = 0.023) was significantly associated with worsened LTC. Seven (6%) patients developed peritumoral edema adverse radiation effects (AREs) at a median time of 35 months (range: 4-182) following SRS. Meningiomas located in supratentorial regions (OR: 1.11, 95% CI: 1.01-1.22, p = 0.031), as compared to skull base tumors, had a significantly greater risk of peritumoral edema ARE development.

CONCLUSIONS

In this select patient cohort, upfront single-session SRS provides durable long-term LTC and minimizes ARE risk for patients with LVMs.

Factors Influencing Long-Term Outcomes of Single-Session Gamma Knife Radiosurgery in Large-Volume Meningiomas &gt;10 cc

INTRODUCTION

Meningiomas are the most common primary intracranial tumour. Gamma knife radiosurgery (GKRS) is a frequently employed non-invasive method of treatment, with good remission rates and low morbidity in literature. However, the role of GKRS in the management of "large" meningiomas is unclear, with reported outcomes that vary by centre. We aimed to assess the factors that influence long-term outcomes following GKRS in meningiomas >10 cc in volume.

METHODS

A retrospectively analysed all patients with meningiomas exceeding 10 cc in volume who underwent GKRS between January 2006 and December 2021 at the National Institute of Mental Health and Neurosciences (NIMHANS), Bengaluru. Demographic, clinical, radiological, and follow-up data were acquired, and factors associated with progression following GKRS were assessed.

RESULTS

The cohort comprised 76 patients 29 males (38.2%) and 47 females (61.8%) with a mean age of 46.3 ± 11.02 years. Thirty-nine patients had been previously operated (51.3%). Meningiomas were most frequently located in the parasagittal region (26 tumours, 34.2%) and sphenopetroclival region (23 tumours, 30.3%), with mean lesion volume of 12.55 ± 5.22 cc, ranging 10.3 cc-25 cc. The mean dose administered to the tumour margin was 12.5 Gy ± 1.2 Gy (range 6-15 Gy). The median duration of clinical follow-up was 48 months, over which period radiological progression occurred in 14 cases (20%), with unchanged tumour volume in 20 cases (28.6%) and reduction in size of the tumour in 36 cases (51.4%). Progression-free survival after GKRS was 72% at 5 years, was significantly poorer among meningiomas with tumour volume >14 cc (log-rank test p = 0.045), tumours presenting with limb motor deficits (log-rank test p = 0.012), and tumours that underwent prior Simpson grade 3 or 4 excision (log-rank test p = 0.032).

CONCLUSIONS

Meningiomas >10 cc in volume appear to display a high rate of progression and subsequent need for surgery following GKRS. Primary surgical resection, when not contraindicated, may be considered with GKRS serving an adjuvant role, especially in tumours exceeding 14 cc in volume, and presenting with limb motor deficits. Long-term clinical and radiological follow-up is essential following GKRS as the response of large meningiomas may be unpredictable.

The role of stereotactic radiosurgery in the management of petroclival meningioma: a systematic review

PURPOSE

Petroclival meningioma (PM) is a challenging neuro oncology case and stereotactic radiosurgery (SRS) is proposed as one treatment option. This systematic review aimed to examine the role of SRS in treating PM cases.

METHODS

 We constructed a systematic review using the PRISMA guidelines using peer-reviewed English literature until 16 February 2022 from EuroPMC and PubMed. We used the terms petroclival meningioma, clival meningioma, apex petrous meningioma, spheno petroclival meningioma, stereotactic radiosurgery, radiosurgery, CyberKnife, Gamma Knife, linear accelerator, LINAC, and radiotherapy.

RESULTS

 10 out of 266 studies were chosen for this systematic review, two of which are case reports. The study comprised 719 patients, 73.7% of whom were female (n = 530) and had a median age of 56.99 years (18-90 years). At the time of diagnosis, the median tumor volume was 6.07 cm³ (0.13-64.9 cm³). The tumors were frequently located near the petroclival junction (83.6%, n = 598). Following SRS, the median follow-up was 64.52 months (3-252 months). 46.5% of 719 PMs exhibited a decrease in tumor size. 46% and 7.5% showed no change and increase in tumor volume, respectively. At the last radiographic follow-up (7-21.2 years), tumor control with a median of 98.8% (85-100%). Complications occurred in 6% of patients, with hydrocephalus (2.2%) as the prevalent complication. The use of SRS as a primary treatment for petroclival cases was not associated with increased complication rate RR 0.62 (95% CI [0.11, 3.59], p = 0.59) but statistically correlated with clinical failure clinical failure RR 0.56 (95% CI [0.32, 0.98], p = 0.04).

CONCLUSIONS

 We found a low number of complications following SRS intervention and has been effectively controlling tumor progression.

Stereotactic Radiosurgery (SRS) Induced Higher-Grade Transformation of a Benign Meningioma into Atypical Meningioma

Background

Stereotactic radiosurgery (SRS) is a widely used treatment modality for the management of meningioma. Whether used as a primary, adjuvant, or salvage procedure, SRS is a safe, less invasive, and effective modality of treatment as microsurgery. The transformation of a meningioma following radiosurgery raises a concern, and our current understanding about it is extremely limited. Only a few case reports have described meningioma dedifferentiation after SRS to a higher grade. Moreover, a relatively small number of cases have been reported in large retrospective studies with little elaboration. Case Description. We report a detailed case description of a 41-year-old man with progressive meningioma enlargement and rapid grade progression after SRS, which was histopathologically confirmed before and after SRS. We discussed the clinical presentation, radiological/histopathological features, and outcome. We also reviewed previous studies that reported the outcome and follow-up of patients diagnosed with grade I meningioma histopathologically or presumed with benign meningioma by radiological features who underwent primary or adjuvant radiosurgery.

Conclusion

The risk of progression after SRS is low, and the risk of higher-grade transformation after SRS is trivial. The early timing for recurrence and field-related radiation may favor a relationship between SRS and higher-grade transformation (causality) although transformation as a part of the natural history of the disease cannot be fully excluded. Tumor progression (treatment failure) after SRS may demonstrate a transformation, and careful, close, and long follow-up is highly recommended. Also, acknowledging that there is a low risk of early and delayed complications and a trivial risk of transformation should not preclude its use as SRS affords a high level of safety and efficiency.

Meningiomas

Meningiomas arise in various locations. Convexity tumors are relatively simple to remove. Skull base tumors and tumors adjacent to the major cerebral veins and venous sinuses can be very difficult to extirpate. Attempts at radical resection can lead to serious morbidity. The combination of bulk reduction using microsurgery followed by GKNS gives greatly improved survival and very low morbidity. With smaller tumors, GKNS may be used as the primary treatment. Increasing numbers of asymptomatic meningiomas are demonstrated either as an unexpected finding or as a residual or recurrent tumor after surgery. In all of these situations, GKNS gives a better result than observation or reoperation.

Vestibular Schwannomas

Vestibular Schwannomas are well treated by GKNS. This can be used alone for tumors up to 20cm³. For larger tumors subtotal, intracapsular resection followed by GKNS a few months later would seem to give the best results. While there remain disagreements relating to optimal treatment for VSs among colleagues using different techniques, there are indications that these are becoming less confrontational. The evidence in this chapter suggests that early GKNS intervention results in better hearing preservation and tumor control in small tumors. The evidence in favor of "wait and see" depends on series reporting on changes in tumor size using suboptimal measurements. It is more important to record the fate of hearing, and this would seem to be better preserved following early GKNS. The results of GKNS for NF2 are by no means as good as could be wished but would seem to be superior to those of microsurgery. The importance of screening of family members cannot be over emphasized.

Single-Session Stereotactic Radiosurgery for Large Benign Meningiomas: Medium-to Long-Term Results

BACKGROUND

The use of stereotactic radiosurgery for the treatment of intracranial meningiomas has been established as an effective and safe treatment modality. Larger meningiomas typically are managed by surgery followed by radiosurgery. 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 the hypofractionation technique. We sought to assess the long-term efficacy and safety of single-session stereotactic radiosurgery for large (10 cc or more) intracranial benign meningiomas.

PATIENTS AND METHODS

In this retrospective study, we included 273 patients with large benign meningiomas (≥10 cc) who were treated by single-session SRS and followed up for more than 2 years. Tumors were in a basal location in 228 patients (84%). There were 161 tumors (59%) in the perioptic location. The median tumor volume was 15.5 (10-57.3 cc [interquartile range {IQR} 12.3 cc]). The median prescription dose was 12 Gy (9-15 Gy [IQR 1 Gy]).

RESULTS

The median follow-up period was 6.1 years (2-18 years [IQR 5.5 years]). The tumor control rate was 90%. The progression-free survival at 5 and 10 years was 96% and 81%, respectively, for the whole cohort. Among 161 patients with perioptic meningiomas, favorable (better/stable) visual outcome was reported in 155 patients (96%) and unfavorable (worse) outcome in 6 patients (4%). Temporary adverse radiation effects were observed in 41 patients (15%) but only 16 (6%) were symptomatic.

CONCLUSIONS

Stereotactic radiosurgery provides an effective and safe treatment option for large meningiomas.

Fractionated Gamma Knife radiosurgery for skull base meningiomas: a single-institution experience

OBJECTIVEGamma Knife radiosurgery (GKRS) has been successfully used for the treatment of intracranial meningiomas given its steep dose gradients and high-dose conformality. However, treatment of skull base meningiomas (SBMs) may pose significant risk to adjacent radiation-sensitive structures such as the cranial nerves. Fractionated GKRS (fGKRS) may decrease this risk, but until recently it has not been practical with traditional pin-based systems. This study reports the authors' experience in treating SBMs with fGKRS, using a relocatable, noninvasive immobilization system.METHODSThe authors performed a retrospective review of all patients who underwent fGKRS for SBMs between 2013 and 2018 delivered using the Extend relocatable frame system or the Icon system. Patient demographics, pre- and post-GKRS tumor characteristics, perilesional edema, prior treatment details, and clinical symptoms were evaluated. Volumetric analysis of pre-GKRS, post-GKRS, and subsequent follow-up visits was performed.RESULTSTwenty-five patients met inclusion criteria. Nineteen patients were treated with the Icon system, and 6 patients were treated with the Extend system. The mean pre-fGKRS tumor volume was 7.62 cm3 (range 4.57-13.07 cm3). The median margin dose was 25 Gy delivered in 4 (8%) or 5 (92%) fractions. The median follow-up time was 12.4 months (range 4.7-17.4 months). Two patients (9%) experienced new-onset cranial neuropathy at the first follow-up. The mean postoperative tumor volume reduction was 15.9% with 6 patients (27%) experiencing improvement of cranial neuropathy at the first follow-up. Median first follow-up scans were obtained at 3.4 months (range 2.8-4.3 months). Three patients (12%) developed asymptomatic, mild perilesional edema by the first follow-up, which remained stable subsequently.CONCLUSIONSfGKRS with relocatable, noninvasive immobilization systems is well tolerated in patients with SBMs and demonstrated satisfactory tumor control as well as limited radiation toxicity. Future prospective studies with long-term follow-up and comparison to single-session GKRS or fractionated stereotactic radiotherapy are necessary to validate these findings and determine the efficacy of this approach in the management of SBMs.

Gamma Knife radiosurgery for intracranial benign meningiomas: follow-up outcome in 130 patients

OBJECTIVEThe authors retrospectively analyzed the follow-up data in 130 patients with intracranial benign meningiomas after Gamma Knife radiosurgery (GKRS), evaluated the tumor progression-free survival (PFS) rate and neurological function preservation rate, and determined the predictors by univariate and multivariate survival analysis.METHODSThis cohort of 130 patients with intracranial benign meningiomas underwent GKRS between May 2012 and May 2015 at the Second Hospital of Tianjin Medical University. The median age was 54.5 years (range 25-81 years), and women outnumbered men at a ratio of 4.65:1. All clinical and radiological data were obtained for analysis. No patient had undergone prior traditional radiotherapy or chemotherapy. The median tumor volume was 3.68 cm3 (range 0.23-45.78 cm3). A median margin dose of 12.0 Gy (range 10.0-16.0 Gy) was delivered to the tumor with a median isodose line of 50% (range 50%-60%).RESULTSDuring a median follow-up of 36.5 months (range 12-80 months), tumor volume regressed in 37 patients (28.5%), was unchanged in 86 patients (66.2%), and increased in 7 patients (5.4%). The actuarial tumor progression-free survival (PFS) rate was 98%, 94%, and 87% at 1, 3, and 5 years, respectively, after GKRS. Tumor recurred in 7 patients at a median follow-up of 32 months (range 12-56 months). Tumor volume ≥ 10 cm3 (p = 0.012, hazard ratio [HR] 8.25, 95% CI 1.60-42.65) and pre-GKRS Karnofsky Performance Scale score < 90 (p = 0.006, HR 9.31, 95% CI 1.88-46.22) were independent unfavorable predictors of PFS rate after GKRS. Of the 130 patients, 101 (77.7%) presented with one or more neurological symptoms or signs before GKRS. Neurological symptoms or signs improved in 40 (30.8%) patients, remained stable in 83 (63.8%), and deteriorated in 7 (5.4%) after GKRS. Two (1.5%) patients developed new cranial nerve (CN) deficit. Tumor volume ≥ 10 cm3 (p = 0.042, HR = 4.73, 95% CI 1.06-21.17) and pre-GKRS CN deficit (p = 0.045, HR = 4.35, 95% CI 0.84-22.48) were independent unfavorable predictors for improvement in neurological symptoms or signs. Six (4.6%) patients developed new or worsening peritumoral edema with a median follow-up of 4.5 months (range 2-7 months).CONCLUSIONSGKRS provided good local tumor control and high neurological function preservation in patients with intracranial benign meningiomas. Patients with tumor volume < 10 cm3, pre-GKRS Karnofsky Performance Scale score ≥ 90, and no pre-GKRS CN deficit (I-VIII) can benefit from stereotactic radiosurgery. It can be considered as the primary or adjuvant management of intracranial benign meningiomas.

Long-Term Outcomes After Linac Radiosurgery for Benign Meningiomas

AIMS

Although several studies on outcomes following stereotactic radiosurgery (SRS) for benign meningiomas have been reported, Linac-based SRS outcomes have not been as widely evaluated. The aim of this retrospective institutional single-centre study was to determine long-term outcomes of Linac-based SRS for benign intracranial meningiomas.

MATERIALS AND METHODS

From July 1996 to May 2011, 60 patients with 69 benign meningiomas were included. All patients were treated with single-fraction Linac-based SRS with four to five non-coplanar arcs, dynamic or not. The marginal dose prescribed for the periphery was 16 Gy. Prognostic factors associated with local control, progression-free survival (PFS) and overall survival were tested.

RESULTS

The median follow-up was 128 months. No patient was lost to follow-up. The values observed at 1, 5 and 10 years were, respectively, 100%, 98.4% and 92.6% for local control, 94.9%, 93.2% and 78% for PFS and 100%, 94.7% and 92.7% for overall survival. In univariate analysis, local control after SRS was significantly higher for skull base and parasagittal meningiomas compared with convexity meningiomas (P = 0.031). Multivariate analyses showed significantly longer PFS when the minimum dose delivered to the tumour was greater than 10 Gy (P = 0.0082). No grade 5 toxicity was reported.

CONCLUSION

Our long-term results from a large sample size of benign meningiomas treated with Linac-based SRS confirmed excellent local control (>90%) and good safety, which is in line with published studies on Gamma Knife surgery. Above all, we showed significantly poorer PFS if the minimum dose to the tumour was under 10 Gy.

Staged Gamma Knife Radiosurgery for Large Skull Base Meningiomas

Purpose: The authors have been treating skull base meningiomas using relatively low-dose gamma knife radiosurgery (GKS, ≤ 12 Gy) with acceptable tumor growth control and low morbidity. In the present study, volume-staged, low-dose GKS was performed for large skull base meningiomas with a maximum diameter > 4 cm. In this article, a treatment strategy for volume-staged GKS and results for large skull base meningiomas are described.

Methods: Data from 27 patients with large skull base meningiomas histopathologically diagnosed as WHO grade I or diagnosed by imaging, who underwent volume-staged GKS between March 1995 and September 2018, were reviewed. Among these patients, 24 were followed-up for > six months. The tumor was located in the parasellar region in nine patients, cavernous sinus region in four, petroclival region in four, petrocavernous sinus region in four, cerebellopontine angle region in two, and in the tent in one. The mean tumor diameters ranged from 31 to 47.8 mm (median 39.4 mm), with tumor volumes between 14.7 and 49.5 cm³ (median 27.5 cm³).

Results: The prescribed radiation dose was 8-12 Gy (median 10 Gy). The treatment interval between the first and second GKS was three to nine months (median 5.5 months). The median duration of follow-up after the first GKS was 84 months (range 6-204 months). Tumor volume decreased in nine (37.5%) patients, remained stable in nine (37.5%), and increased (local failure) in six (25%). The actuarial progression-free local control rate was 88% at three years, 78% at five years, 70% at 10 years, and 70% at 15 years. Neurological status improved in three (12.5%) patients, was unchanged in 16 (66.5%), and deteriorated in five (21%). Permanent radiation injury occurred in one (4%) patient.

Conclusion: Volume-staged GKS demonstrated the usefulness for large skull meningiomas > 4 cm in diameter, over a long-term follow-up period.

Stereotactic Radiosurgery for Large Benign Intracranial Tumors

BACKGROUND

Historically, it is stated that large intracranial tumors, herein defined as a maximum dimension of ≥3 cm or tumor volume ≥14.2 cm³, are not candidates for stereotactic radiosurgery (SRS). We report outcomes of patients with large benign intracranial tumors treated with SRS.

METHODS

With institutional review board approval, we retrospectively identified 74 patients with large benign intracranial tumors (59 meningiomas, 9 vestibular schwannomas, and 6 glomus jugulare tumors) treated with robotic SRS (2007-2018). Patients received definitive SRS in 47.3% of the cases, adjuvant to surgical resection in 44.6%, and salvage after past radiation treatment in 8.1%. A median tumor volume of 16.0 cm³ (range, 10.1-65.5 cm³) received a median dose of 24.0 Gy (range, 14.0-30.0 Gy) in a median of 3 fractions (range, 1-5), for a median single fraction equivalent dose (with alpha/beta of 3) of 14.8 Gy (range, 11.3-18.0 Gy). The Kaplan-Meier estimate of tumor local control (LC) was calculated from date of SRS.

RESULTS

With a median clinical follow-up of 32.8 months (range, 0.6-125.9 months) and median radiologic follow-up of 28.5 months (range, 0.6-121.4 months), LC was 96.5% (95% confidence interval, 92.4%-100%) at 3 years and 91.7% (95% confidence interval, 87.6%-95.7%) at 5 years. Adverse radiation effect (ARE) was seen in 10 patients (13.5%) at a median of 13.5 months (range, 7.8-34.5 months). ARE occurred in 9% of those with prior treatment compared with 5% who were radiation-naïve (P = 0.23). With 236.4 person-years of follow-up, no secondary malignancies were seen.

CONCLUSIONS

Despite the historical adage, we find that SRS provides high rates of LC for these large tumors, with rates of ARE similar to historical reports of SRS for smaller benign tumors.

Gamma Knife Radiosurgery for Anterior Clinoid Process Meningiomas: A Series of 61 Consecutive Patients

OBJECTIVE

Gamma Knife radiosurgery (GKRS) outcomes for anterior clinoid process (ACP) meningiomas have not been specifically reported within any meningioma series. We present the initial and largest series in the literature that describes the presenting features, radiosurgery parameters, and radiologic and long-term clinical outcomes for 61 patients with ACP meningiomas treated with GKRS.

METHODS

Medical records were reviewed for 61 consecutive patients at a single center who underwent GKRS for ACP meningioma between 2008 and 2016.

RESULTS

Of 61 patients with ACP meningiomas, 49 (80%) were treated with GKRS as primary treatment, and 12 (20%) were treated with GKRS as an adjuvant therapy. Before GKRS, 29 patients presented with visual impairment and 50 patients presented with headache. Median patient age was 54.9 years. Median tumor volume was 3.2 cm³, and median margin dose was 12.0 Gy. The median radiologic follow-up time after GKRS was 75 months. During follow-up, tumor volume regressed in 37 cases (61%) and remained unchanged in 24 cases (39%). None of the patients experienced tumor volume progression. Tumor volume <3 cm³ was an independent predictor of tumor volume regression after GKRS (univariate analysis, P = 0.047; multivariate analysis, P = 0.049). Of 29 patients who presented with visual impairment, 16 (55%) improved after GKRS. None of the 61 patients developed new neurologic deficits after GKRS.

CONCLUSIONS

GKRS provides a high rate of tumor volume control for ACP meningiomas as well as a low complication rate. Excellent tumor volume control was associated with smaller tumor size only.

Stereotactic Radiosurgery in Large Intracranial Meningiomas: A Systematic Review

Gross total resection of large intracranial meningiomas (LIMs) can be challenging and cause significant morbidity and mortality. The aim of this systematic review is to determine the clinical effectiveness and safety of stereotactic radiosurgery (SRS) either as primary or adjuvant therapy for LIMs with tumors ≥2.5 cm in maximum dimension (tumor volume ≥8.1 cm³). A total of 452 tumors in 496 patients (350 female [69.3%] and 146 male [30.6%]) with median age 60 years (48-65 years) were included. The median tumor volume at the time of diagnosis was 16.7 cm³ (10-53.3 cm³). The tumors typically were located in the skull base (77.2%), whereas only 14.6% were in the supratentorial space. The median follow-up after SRS was 54 months (18-90 months). In total, 87.8% of patients were treated with single-session (SS) Gamma Knife radiosurgery (GKS), whereas the remaining 12.1% patients received non-SS GKS. Of 452 LIMs assessed for clinical response, 45.1% showed improvement and 15.7% deteriorated after SRS. Radiographic tumor control at last follow-up (2-7.5 years) ranged from 84% to 100%. Overall, radiation-induced toxicity occurred in 23% of patients, with the most common adverse effect being cranial nerve neuropathy (5.5%) and peritumoral edema (5.3%). Subgroup analysis revealed that there is 2-fold greater likelihood of improvement in clinical symptoms in patients with non-SS GKS than SS GKS (odds ratio 2.47; 95% confidence interval 1.38-4.44; P = 0.002). SRS is safe and effective in the treatment of LIMs as primary or adjuvant treatment. Further prospective studies are required to validate our results.

Forward treatment planning techniques to reduce the normalization effect in Gamma Knife radiosurgery

In Gamma Knife forward treatment planning, normalization effect may be observed when multiple shots are used for treating large lesions. This effect can reduce the proportion of coverage of high‐value isodose lines within targets. The aim of this study was to evaluate the performance of forward treatment planning techniques using the Leksell Gamma Knife for the normalization effect reduction. We adjusted the shot positions and weightings to optimize the dose distribution and reduce the overlap of high‐value isodose lines from each shot, thereby mitigating the normalization effect during treatment planning. The new collimation system, Leksell Gamma Knife Perfexion, which contains eight movable sectors, provides an additional means to reduce the normalization effect by using composite shots. We propose different techniques in forward treatment planning that can reduce the normalization effect. Reducing the normalization effect increases the coverage proportion of higher isodose lines within targets, making the high‐dose region within targets more uniform and increasing the mean dose to targets. Because of the increase in the mean dose to the target after reducing the normalization effect, we can set the prescribed marginal dose at a higher isodose level and reduce the maximum dose, thereby lowering the risk of complications.

Stereotactic radiosurgery in the treatment of parasellar meningiomas: long-term volumetric evaluation

OBJECTIVE Parasellar meningiomas tend to invade the suprasellar, cavernous sinus, and petroclival regions, encroaching on adjacent neurovascular structures. As such, they prove difficult to safely and completely resect. Stereotactic radiosurgery (SRS) has played a central role in the treatment of parasellar meningiomas. Evaluation of tumor control rates at this location using simplified single-dimension measurements may prove misleading. The authors report the influence of SRS treatment parameters and the timing and volumetric changes of benign WHO Grade I parasellar meningiomas after SRS on long-term outcome. METHODS Patients with WHO Grade I parasellar meningiomas treated with single-session SRS and a minimum of 6 months of follow-up were selected. A total of 189 patients (22.2% males, n = 42) form the cohort. The median patient age was 54 years (range 19-88 years). SRS was performed as a primary upfront treatment for 44.4% (n = 84) of patients. Most (41.8%, n = 79) patients had undergone 1 resection prior to SRS. The median tumor volume at the time of SRS was 5.6 cm³ (0.2-54.8 cm³). The median margin dose was 14 Gy (range 5-35 Gy). The volumes of the parasellar meningioma were determined on follow-up scans, computed by segmenting the meningioma on a slice-by-slice basis with numerical integration using the trapezoidal rule. RESULTS The median follow-up was 71 months (range 6-298 months). Tumor volume control was achieved in 91.5% (n = 173). Tumor progression was documented in 8.5% (n = 16), equally divided among infield recurrences (4.2%, n = 8) and out-of-field recurrences (4.2%, n = 8). Post-SRS, new or worsening CN deficits were observed in 54 instances, of which 19 involved trigeminal nerve dysfunction and were 18 related to optic nerve dysfunction. Of these, 90.7% (n = 49) were due to tumor progression and only 9.3% (n = 5) were attributable to SRS. Overall, this translates to a 2.64% (n = 5/189) incidence of direct SRS-related complications. These patients were treated with repeat SRS (6.3%, n = 12), repeat resection (2.1%, n = 4), or both (3.2%, n = 6). For patients treated with a margin dose ≥ 16 Gy, the 2-, 4-, 6-, 8-, 10-, 12-, and 15-year actuarial progression-free survival rates are 100%, 100%, 95.7%, 95.7%, 95.7%, 95.7%, and 95.7%, respectively. Patients treated with a margin dose < 16 Gy, had 2-, 4-, 6-, 8-, 10-, 12-, and 15-year actuarial progression-free survival rates of 99.4%, 97.7%, 95.1%, 88.1%, 82.1%, 79.4%, and 79.4%, respectively. This difference was deemed statistically significant (p = 0.043). Reviewing the volumetric patient-specific measurements, the early follow-up volumetric measurements (at the 3-year follow-up) reliably predicted long-term volume changes and tumor volume control (at the 10-year follow-up) (p = 0.029). CONCLUSIONS SRS is a durable and minimally invasive treatment modality for benign parasellar meningiomas. SRS offers high rates of growth control with a low incidence of neurological deficits compared with other treatment modalities for meningiomas in this region. Volumetric regression or stability during short-term follow-up of 3 years after SRS was shown to be predictive of long-term tumor control.

Prognostic value of diffusion tensor imaging parameters for Gamma Knife radiosurgery in meningiomas

OBJECTIVE

Diffusion tensor imaging (DTI) parameters are able to differentiate between meningioma subtypes. The hypothesis that there is a correlation between DTI parameters and the change in tumor size after Gamma Knife radiosurgery (GKRS) was analyzed.

METHODS

DTI parameters were measured using MRI before GKRS in 26 patients with meningiomas. The findings were correlated with the change in tumor size after treatment as measured at the last follow-up (range 12.5–45 months).

RESULTS

Only those meningiomas that showed the highest fractional anisotropy (FA), the lowest spherical index of the tensor ellipsoid (Cs), and the lowest radial diffusivity (RD) either increased or remained stable in terms of volume, whereas all other meningiomas decreased in volume. The correlation between the DTI parameters (correlation values of −0.81 for FA, 0.75 for Cs, 0.66 for RD, and 0.66 for mean diffusivity) and the rate of volume change per month was significant (p ≤ 0.001). Other factors, including original tumor size, prescription dose, and patient age, did not correlate significantly.

CONCLUSIONS

Meningiomas that show high FA values—as well as low Cs, low RD, and low mean diffusivity values—do not respond as well to GKRS in comparison with meningiomas with low FA values. This finding might be due to their higher content level of fibrous tissue. In particular, the meningioma with the highest FA value (0.444) considerably increased in volume (by 32.3% after 37 months), whereas the meningioma with the lowest FA value (0.151) showed the highest rate of reduction (3.3% per month) in this study.

Successful CyberKnife Irradiation of 1000 cc Hemicranial Meningioma: 6-year Follow-up

Meningiomas are common benign tumors with accepted treatment approaches and usually don't challenge healthcare specialists. We present a case of a huge unresectable hemicranial meningioma, which was successfully treated with hypofractionated irradiation.

A male patient, sixty-two years of age, suffered for over 12 years from headaches, facial deformity, right eye displacement, right eye movement restriction, right-sided ptosis, and facial hypoesthesia. MRI and CT studies revealed an extended hemicranial meningioma. Prior to irradiation, the patient underwent four operations. Eventually, the tumor was irradiated with the CyberKnife in August 2009. Tumor volume composed 1085 cc. The mean dose of 35.3 Gy was delivered in 7 fractions (31.5 Gy at 72% isodose line comprising 95% of tumor volume). The patient was followed during six years and experienced only mild (Grade 1-2 CTCAE) acute skin and mucosa reactions. During the follow-up period, we observed target volume shrinkage for 17% (for 26% after excluding hyperostosis) and regression of intracranial hypertension signs.

Due to the extreme volume and complex shape of the tumor, spreading along the surface of the hemisphere as well as an optic nerve involvement, the case presented would not be generally considered suitable for irradiation, especially for hypofractionation. We regard this clinical situation not as a treatment recommendation, but as a demonstration of the underestimated possibilities of hypofractionation regimen and CyberKnife system, both of which are limited with our habit of conventional treatments.

The cavernous sinus meningiomas' dilemma: Surgery or stereotactic radiosurgery?

Despite the advances in techniques and technologies, the management of cavernous sinus (CS) meningiomas still remains a challenge for both neurosurgeons and radiation oncologists. On the other hand, the improvement of the anatomical knowledge and the microsurgical techniques together with diffusion of radiosurgery are currently changing the treatment strategy, opening new perspectives to the patients which are suffering from such lesions. The authors reviewed here the literature data. A multidisciplinary treatment algorithm is also proposed.

Gamma Knife radiosurgery of large skull base meningiomas

OBJECT

Stereotactic radiosurgery (SRS) has become a common treatment modality for intracranial meningiomas. Skull base meningiomas greater than 8 cm3 in volume have been found to have worse outcomes following SRS. When symptomatic, patients with these tumors are often initially treated with resection. For tumors located in close proximity to eloquent structures or in patients unwilling or unable to undergo a resection, SRS may be an acceptable therapeutic approach. In this study, the authors review the SRS outcomes of skull base meningiomas greater than 8 cm3 in volume, which corresponds to a lesion with an approximate diameter of 2.5 cm.

METHODS

The authors reviewed the data in a prospectively compiled database documenting the outcomes of 469 patients with skull base meningiomas treated with single-session Gamma Knife radiosurgery (GKRS). Seventy-five patients had tumors greater than 8 cm3 in volume, which was defined as a large tumor. All patients had a minimum follow-up of 6 months, but patients were included if they had a complication at any time point. Thirty patients were treated with upfront GKRS, and 45 were treated following microsurgery. Patient and tumor characteristics were assessed to determine predictors of new or worsening neurological function and tumor progression following GKRS.

RESULTS

After a mean follow-up of 6.5 years (range 0.5–21 years), the tumor volume was unchanged in 37 patients (49%), decreased in 26 patients (35%), and increased in 12 patients (16%). Actuarial rates of progression-free survival at 3, 5, and 10 years were 90.3%, 88.6%, and 77.2%, respectively. Four patients had new or worsened edema following GKRS, but preexisting edema decreased in 3 patients. In Cox multivariable analysis, covariates associated with tumor progression were 1) presentation with any cranial nerve (CN) deficit from III to VI (hazard ratio [HR] 3.78, 95% CI 1.91–7.45; p < 0.001), history of radiotherapy (HR 12.06, 95% CI 2.04–71.27; p = 0.006), and tumor volume greater than 14 cm3 (HR 6.86, 95% CI 0.88–53.36; p = 0.066). In those patients with detailed clinical follow-up (n = 64), neurological function was unchanged in 37 patients (58%), improved in 16 patients (25%), and deteriorated in 11 patients (17%). In multivariate analysis, the factors predictive of new or worsening neurological function were history of surgery (OR 3.00, 95% CI 1.13–7.95; p = 0.027), presentation with any CN deficit from III to VI (OR 3.94, 95% CI 1.49–10.24; p = 0.007), and decreasing maximal dose (OR 0.76, 95% CI 0.63–0.93; p = 0.007). Tumor progression was present in 64% of patients with new or worsening neurological decline.

CONCLUSIONS

Stereotactic radiosurgery affords a reasonable rate of tumor control for large skull base meningiomas and does so with a low incidence of neurological deficits. Those with a tumor less than 14 cm3 in volume and without presenting CN deficit from III to VI were more likely to have effective tumor control.

Stereotactic radiosurgery of meningiomas following resection: predictors of progression

Residual or recurrent meningiomas after initial surgical resection are commonly treated with stereotactic radiosurgery (SRS), but progression of these tumors following radiosurgery is difficult to predict. We performed a retrospective review of 60 consecutive patients who underwent resection and subsequent Gamma Knife (Elekta AB, Stockholm, Sweden) radiosurgery for residual or recurrent meningiomas at our institution from 2001-2012. Patients were subdivided by Simpson resection grade and World Health Organization (WHO) grade. Cox multivariate regression and Kaplan-Meier analyses were performed to assess risk of tumor progression. There were 45 men (75%) and 15 women (25%) with a median age of 56.8 years (range 26.5-82 years). The median follow-up period was 34.9 months (range 6-108.4 months). Simpson grade 1-3 resection was achieved in 17 patients (28.3%) and grade 4 resection in 43 patients (71.7%). Thirty-four tumors (56.7%) were WHO grade 1, and 22 (36.7%) were WHO grade 2-3. Time from resection to SRS was significantly shorter in patients with Simpson grade 4 resection compared to grade 1-3 resection (p<0.01), but did not differ by WHO grade (p=0.17). Post-SRS complications occurred in five patients (8.3%). Overall, 19 patients (31.7%) experienced progression at a median of 15.3 months (range 1.2-61.4 months). Maximum tumor diameter >2.5 cm at the time of SRS (p=0.02) and increasing WHO grade (p<0.01) were predictive of progression in multivariate analysis. Simpson resection grade did not affect progression-free survival (p=0.90). The mortality rate over the study period was 8.3%. SRS offers effective tumor control for residual or recurrent meningiomas following resection, especially for small benign tumors.

Gamma Knife radiosurgery for sellar and parasellar meningiomas: a multicenter study

Object

Parasellar and sellar meningiomas are challenging tumors owing in part to their proximity to important neurovascular and endocrine structures. Complete resection can be associated with significant morbidity, and incomplete resections are common. In this study, the authors evaluated the outcomes of parasellar and sellar meningiomas managed with Gamma Knife radiosurgery (GKRS) both as an adjunct to microsurgical removal or conventional radiation therapy and as a primary treatment modality.

Methods

A multicenter study of patients with benign sellar and parasellar meningiomas was conducted through the North American Gamma Knife Consortium. For the period spanning 1988 to 2011 at 10 centers, the authors identified all patients with sellar and/or parasellar meningiomas treated with GKRS. Patients were also required to have a minimum of 6 months of imaging and clinical follow-up after GKRS. Factors predictive of new neurological deficits following GKRS were assessed via univariate and multivariate analyses. Kaplan-Meier analysis and Cox multivariate regression analysis were used to assess factors predictive of tumor progression.

Results

The authors identified 763 patients with sellar and/or parasellar meningiomas treated with GKRS. Patients were assessed clinically and with neuroimaging at routine intervals following GKRS. There were 567 females (74.3%) and 196 males (25.7%) with a median age of 56 years (range 8–90 years). Three hundred fifty-five patients (50.7%) had undergone at least one resection before GKRS, and 3.8% had undergone prior radiation therapy. The median follow-up after GKRS was 66.7 months (range 6–216 months). At the last follow-up, tumor volumes remained stable or decreased in 90.2% of patients. Actuarial progression-free survival rates at 3, 5, 8, and 10 years were 98%, 95%, 88%, and 82%, respectively. More than one prior surgery, prior radiation therapy, or a tumor margin dose < 13 Gy significantly increased the likelihood of tumor progression after GKRS.

At the last clinical follow-up, 86.2% of patients demonstrated no change or improvement in their neurological condition, whereas 13.8% of patients experienced symptom progression. New or worsening cranial nerve deficits were seen in 9.6% of patients, with cranial nerve (CN) V being the most adversely affected nerve. Functional improvements in CNs, especially in CNs V and VI, were observed in 34% of patients with preexisting deficits. New or worsened endocrinopathies were demonstrated in 1.6% of patients; hypothyroidism was the most frequent deficiency. Unfavorable outcome with tumor growth and accompanying neurological decline was statistically more likely in patients with larger tumor volumes (p = 0.022) and more than 1 prior surgery (p = 0.021).

Conclusions

Gamma Knife radiosurgery provides a high rate of tumor control for patients with parasellar or sellar meningiomas, and tumor control is accompanied by neurological preservation or improvement in most patients.

A hybrid PDMS-Parylene subdural multi-electrode array

In this paper, we report on a cost effective and simple method for fabricating a flexible multi-electrode array for subdural neural recording. The electrode was fabricated using a PDMS-Parylene bilayer to combine the major advantages of both materials. Mechanical and electrical characterizations were performed to confirm functionality of a 16-site electrode array under various flexed/bent conditions. The electrode array was helically wound around a 3 mm diameter cylindrical tube and laid over a 2 cm diameter sphere while maintaining its recording capability. Experimental results showed impedance values between 300 kΩ and 600 kΩ at 1 kHz for 90 μm diameter gold recording sites. Acoustically evoked neural activity was successfully recorded from rat auditory cortex, confirming in vivo functionality.

Concept of robotic gamma knife microradiosurgery and results of its clinical application in benign skull base tumors

The availability of advanced computer-aided robotized devices for the Gamma Knife (i.e., an automatic positioning system and PerfeXion) resulted in significant changes in radiosurgical treatment strategy. The possibility of applying irradiation precisely and the significantly improved software for treatment planning led to the development of the original concept of robotic Gamma Knife microradiosurgery, which is comprised of the following: (1) precise irradiation of the lesion with regard to conformity and selectivity; (2) intentional avoidance of excessive irradiation of functionally important anatomical structures, particularly cranial nerves, located both within the target and in its vicinity; (3) delivery of sufficient radiation energy to the tumor with a goal of shrinking it while keeping the dose at the margins low enough to prevent complications. Realization of such treatment principles requires detailed evaluation of the microanatomy of the target area, which is achieved with an advanced neuroimaging protocol. From 2003, we applied the described microradiosurgical concept in our clinic for patients with benign skull base tumors. Overall, 75 % of neoplasms demonstrated shrinkage, and 47 % showed ≥50 % and more volume reduction. Treatment-related complications were encountered in only 6 % of patients and were mainly related to transient cranial nerve palsy. Just 2 % of neoplasms showed regrowth after irradiation. In conclusion, applying the microradiosurgical principles based on advanced neuroimaging and highly precise treatment planning is beneficial for patients, providing a high rate of tumor shrinkage and a low morbidity rate.

[Stereotactic radiotherapy of intracranial benign tumors]

Stereotactic radiotherapy can be delivered in one fraction or in multiple fractions schedule. It is used in benign tumours such as meningiomas, mainly localized in the base of the skull, for acoustic schwannoma and pituitary tumours. Whatever the tumour, results with the Gamma Knife(®) are the most numerous, but those obtained by linear accelerators, adapted or dedicated, are comparable. The peripheral dose is preferred to the dose delivered to the isocentre. One fraction stereotactic irradiation should be proposed in small lesions and fractionated treatment for tumours larger. Whatever the tumour, the results are satisfactory with a control rate of 90%. However, this value reflects a disparity assessment, radiological stability for meningiomas, radiological stability and preservation of useful hearing in schwannoma and radiological stability and a decrease in hormonal secretions for pituitary adenomas. Overall complication rates are low. In total, the treatment of benign lesions with stereotactic irradiation gives satisfactory results with few complications.

Gamma knife surgery for skull base meningiomas

OBJECT

Skull base meningiomas are challenging tumors owing in part to their close proximity to important neurovascular structures. Complete microsurgical resection can be associated with significant morbidity, and recurrence rates are not inconsequential. In this study, the authors evaluate the outcomes of skull base meningiomas treated with Gamma Knife surgery (GKS) both as an adjunct to microsurgery and as a primary treatment modality.

METHODS

The authors performed a retrospective review of a prospectively compiled database detailing the outcomes in 255 patients with skull base meningiomas treated at the University of Virginia from 1989 to 2006. All patients had a minimum follow-up of 24 months. The group comprised 54 male and 201 female patients, with a median age of 55 years (range 19-85 years). One hundred nine patients were treated with upfront radiosurgery, and 146 patients were treated with GKS following resection. Patients were assessed clinically and radiographically at routine intervals following GKS. Factors predictive of new neurological deficit following GKS were assessed via univariate and multivariate analysis, and Kaplan-Meier analysis and Cox multivariate regression analysis were used to assess factors predictive of tumor progression.

RESULTS

Meningiomas were centered over the cerebellopontine angle in 43 patients (17%), the clivus in 40 (16%), the petroclival region in 28 (11%), the petrous region in 6 (2%), and the parasellar region in 138 (54%). The median duration of follow-up was 6.5 years (range 2-18 years). The mean preradiosurgery tumor volume was 5.0 cm(3) (range 0.3-54.8 cm(3)). At most recent follow-up, 220 patients (86%) displayed either no change or a decrease in tumor volume, and 35 (14%) displayed an increase in volume. Actuarial progression-free survival at 3, 5, and 10 years was 99%, 96%, and 79%, respectively. In Cox multivariate analysis, pre-GKS covariates associated with tumor progression included age greater then 65 years (HR 3.41, 95% CI 1.63-7.13, p = 0.001) and decreasing dose to tumor margin (HR 0.90, 95% CI 0.80-1.00, p = 0.05). At most recent clinical follow-up, 230 patients (90%) demonstrated no change or improvement in their neurological condition and the condition of 25 patients had deteriorated (10%). In multivariate analysis, the factors predictive of new or worsening symptoms were increasing duration of follow-up (OR 1.01, 95% CI 1.00-1.02, p = 0.015), tumor progression (OR 2.91, 95% CI 1.60-5.31, p < 0.001), decreasing maximum dose (OR 0.90, 95% CI 0.84-0.97, p = 0.007), and petrous or clival location versus parasellar, petroclival, and cerebellopontine angle location (OR 3.47, 95% CI 1.23-9.74, p = 0.018).

CONCLUSIONS

Stereotactic radiosurgery offers a high rate of tumor control and neurological preservation in patients with skull base meningiomas. After radiosurgery, better outcomes were observed for those receiving an optimal radiosurgery dose and harboring tumors located in a cerebellopontine angle, parasellar, or petroclival location.

What Factors Predict the Response of Larger Brain Metastases to Radiosurgery?

BACKGROUND:

Approximately 20 to 40% of patients with systemic malignancies develop brain metastases.

OBJECTIVE:

To assess the potential role of stereotactic radiosurgery (SRS) for larger metastatic brain tumors, we reviewed our recent experience.

METHODS:

Between 2004 and 2008, 70 patients with a metastatic brain tumor larger than 3 cm in maximum diameter underwent Gamma knife SRS. Thirty-three patients had received previous whole brain radiation therapy (WBRT) and 37 received only SRS.

RESULTS:

The overall median follow-up was 8.1 months. At the first planned imaging follow-up at 2 months, 29 (41%) tumors had &gt;50% volume reduction, 22 (31%) had 10 to 50% volume reduction, and 19 (28%) were stable or larger. We also evaluated brain edema using MRI T2 images. In 11 patients (16%) the peritumoral edema volume was reduced by more than 50%, in 25 (36%) it was reduced by 10 to 50%, in 21 (30%) it was stable, and in 13 (19%) it was increased. Twenty (36%) discontinued corticosteroids by the time of first imaging follow-up. Because of persistent symptoms, 7 patients (10%) required a craniotomy to remove the tumor. Tumor volume reduction (&gt;50%) was associated with a single metastasis (P = .012), no previous WBRT (P = .002), and a tumor volume &lt;16 cm3 (P = .002). The better peritumoral edema volume reduction (&gt;50%) was associated with a single metastasis (P = .024), no previous WBRT (P = .05), and breast cancer histology (P = .044).

CONCLUSION:

Surgical resection remains the primary approach for larger brain metastases if feasible. Tumor volume is a better indicator than maximum diameter. Tumor volume and edema responded better in patients who underwent SRS alone.

Long-term outcomes of stereotactic radiosurgery for treatment of cavernous sinus meningiomas

PURPOSE

Patients with cavernous sinus meningiomas (CSM) have an elevated risk of surgical morbidity and mortality. Recurrence is often observed after partial resection. Stereotactic radiosurgery (SRS), either alone or combined with surgery, represents an important advance in CSM management, but long-term results are lacking.

METHODS AND MATERIALS

A total of 88 CSM patients, treated from January 1991 to December 2005, were retrospectively reviewed. The mean follow-up was 86.8 months (range, 17.1-179.4 months). Among the patients, 22 were followed for more than 10 years. There was a female predominance (84.1%). The age varied from 16 to 90 years (mean, 51.6). In all, 47 patients (53.4%) received SRS alone, and 41 patients (46.6%) had undergone surgery before SRS. A dose of 14 Gy was prescribed to isodose curves from 50% to 90%. In 25 patients (28.4%), as a result of the proximity to organs at risk, the prescribed dose did not completely cover the target.

RESULTS

After SRS, 65 (73.8%) patients presented with tumor volume reduction; 14 (15.9%) remained stable, and 9 (10.2%) had tumor progression. The progression-free survival was 92.5% at 5 years, and 82.5% at 10 years. Age, sex, maximal diameter of the treated tumor, previous surgery, and complete target coverage did not show significant associations with prognosis. Among the 88 treated patients, 17 experienced morbidity that was related to SRS, and 6 of these patients spontaneously recovered.

CONCLUSIONS

SRS is an effective and safe treatment for CSM, feasible either in the primary or the postsurgical setting. Incomplete coverage of the target did not worsen outcomes. More than 80% of the patients remained free of disease progression during long-term follow-up.

Stereotactic radiosurgery for WHO grade I meningiomas

Meningiomas represent a common intracranial tumor in the adult population. Although extirpation to achieve a gross total resection or at least decrease mass effect has been the mainstay of treatment, stereotactic radiosurgery has come to play an increasingly important role in the management of patients with meningiomas. Radiosurgery utilizes highly focused, beams of ionizing radiation to inactivate tumor cells. Image guidance and a steep dose fall off are critical features of this approach. The radiobiology of radiosurgery differs in certain advantageous ways from conventional radiotherapy. Radiosurgery initially was utilized to treat recurrent or residual skull base meningiomas. As success was observed in this setting, radiosurgery has gradually expanded its role so as to treat convexity meningiomas; it is also used as an upfront treatment for patients for whom clinical and neuro-imaging findings are consistent with a meningioma. Most large series demonstrate tumor control rates for patients with grade I meningiomas in excess of 85%. Neurological function is generally preserved or improved for patients with meningiomas. However, complications can occur. Longitudinal follow-up including neurologic and radiologic assessment is required. Single and multisession stereotactic radiosurgery will likely play an expanded role in the treatment of patients with meningiomas.

Radiotherapy and radiosurgery for benign skull base meningiomas

Meningiomas located in the region of the base of skull are difficult to access. Complex combined surgical approaches are more likely to achieve complete tumor removal, but frequently at a cost of treatment related high morbidity. Local control following subtotal excision of benign meningiomas can be improved with conventional fractionated external beam radiation therapy with a reported 5-year progression-free survival up to 95%. New radiation techniques, including stereotactic radiosurgery (SRS), fractionated stereotactic radiotherapy (FSRT), and intensity-modulated radiotherapy (IMRT) have been developed as a more accurate technique of irradiation with more precise tumor localization, and consequently a reduction in the volume of normal brain irradiated to high radiation doses. SRS achieves a high tumour control rate in the range of 85-97% at 5 years, although it should be recommended only for tumors less than 3 cm away more than 3 mm from the optic pathway because of high risk of long-term neurological deficits. Fractionated RT delivered as FSRT, IMRT and protons is useful for larger and irregularly or complex-shaped skull base meningiomas close to critical structures not suitable for single-fraction SRS. The reported results indicate a high tumour control rate in the range of 85-100% at 5 years with a low risk of significant incidence of long-term toxicity. Because of the long natural history of benign meningiomas, larger series and longer follow-up are necessary to compare results and toxicity of different techniques.