Results of linear accelerator-based radiosurgery for intracranial meningiomas

Radiosurgery in Grade II and III Meningiomas: A Systematic Review and Meta-Analysis

BACKGROUND

Meningiomas are the most prevalent benign intracranial tumors. When they are of the invasive subtypes, i.e., grades II and III, they can recur rapidly and present a real challenge for physicians. This study is focused on the use of stereotactic radiosurgery to manage high-grade meningiomas.

METHOD

Medline via PubMed was searched from inception to December 2022 to retrieve studies on stereotactic radiation therapy for patients with grade II-III meningiomas. This study was conducted under PRISMA guidelines.

RESULT

A total of 29 articles involving 1446 patients with grade II-III meningiomas treated with stereotactic radiation therapy were included in the present study. Of these studies, 11 were conducted exclusively on patients with atypical meningiomas (grade II), 1 targeted anaplastic meningiomas (grade III), and 17 articles were carried out on both grade II and III meningiomas. The pooled 1, 2, 3, 5, and 10-year overall survival (OS) of grade II meningiomas was 0.96 [p < 0.01], 0.89 [p = 0.01], 0.90 [p = 0.09], 0.81 [p < 0.01], and 0.66 [p = 0.55], respectively. The pooled 2, 5, and 10-year OS of grade III meningiomas was 0.64 [p = 0.01], 0.41 [p = 0.01], and 0.19 [p < 0.01], respectively.

CONCLUSIONS

Although long-term prospective studies are still required, the outcomes of stereotactic radiation therapy appear promising regarding overall outcome and progression-free survival.

Bibliometric analysis of the top 100 cited articles on stereotactic radiosurgery of intracranial meningiomas

BACKGROUND

Sterotactic radiosurgery is becoming an integral modality in the management of intracranial meningiomas, both as the primary treatment or as adjuvant therapy. This study analyzes the scholarly impact of the top 100 cited articles on the stereotactic radiosurgical management of intracranial meningiomas.

METHODS

A ranked list of the 100 most-cited articles was generated using the Scopus database by searching the keywords 'intracranial meningioma' and 'stereotactic radiosurgery'. All articles were then evaluated on multiple criteria regarding both the publication of the articles (year of publication, journal, country of origin, and authors) as well as their methods and foci (type of study, location of studied meningiomas, and type of radiosurgical modality). Quantitaitve and qualitative analyses were then performed from the collected data.

RESULTS

The most frequently cited articles on stereotactic radiosurgical management of intracranial meningiomas were published between 1990 and 2016. The average citation-per-year across all papers in the list was 6.1. The most studied anatomic area of intracranial meningiomas was the skull base, with the cavernous sinus being the most well-studied specific site. The most utilized stereotactic radiosurgical modality was Gamma Knife radiosurgery. The country with the highest number of publications was the United States. Twenty-six percent of the articles were published in the journal Neurosurgery; Lunsford, Kondziolka, Flickinger, Sheehan, and Pollock were respectively the most frequent listed authors among this list. The most active academic institute publishing on this topic was the University of Pittsburgh Medical Center.

CONCLUSION

Stereotactic radiosurgery is an integral modality in the management of intracranial meningiomas. This bibliometric analysis sheds the light on the ways in which intracranial meningiomas have been studied in the past two decades in order to identify trends among neurosurgeons and radiation oncologists and to reveal areas of rising and declining focus.

Stereotactic Radiosurgery for Benign Cavernous Sinus Meningiomas: A Multicentre Study and Review of the Literature

Cavernous sinus meningiomas (CSMs) remain a surgical challenge due to the intimate involvement of their contained nerves and blood vessels. Stereotactic radiosurgery (SRS) is a safe and effective minimally invasive alternative for the treatment of small- to medium-sized CSMs. Objective: To assess the medium- to long-term outcomes of SRS for CSMs with respect to tumour growth, prevention of further neurological deterioration and improvement of existing neurological deficits. This multicentric study included data from 15 European institutions. We performed a retrospective observational analysis of 1222 consecutive patients harbouring 1272 benign CSMs. All were treated with Gamma Knife stereotactic radiosurgery (SRS). Clinical and imaging data were retrieved from each centre and entered into a common database. All tumours with imaging follow-up of less than 24 months were excluded. Detailed results from 945 meningiomas (86%) were then analysed. Clinical neurological outcomes were available for 1042 patients (85%). Median imaging follow-up was 67 months (mean 73.4, range 24-233). Median tumour volume was 6.2 cc (+/-7), and the median marginal dose was 14 Gy (+/-3). The post-treatment tumour volume decreased in 549 (58.1%), remained stable in 336 (35.6%) and increased in only 60 lesions (6.3%), yielding a local tumour control rate of 93.7%. Only 27 (2.8%) of the 60 enlarging tumours required further treatment. Five- and ten-year actuarial progression-free survival (PFS) rates were 96.7% and 90.1%, respectively. Tumour control rates were higher for women than men (p = 0.0031), and also for solitary sporadic meningiomas (p = 0.0201). There was no statistically significant difference in outcome for imaging-defined meningiomas when compared with histologically proven WHO Grade-I meningiomas (p = 0.1212). Median clinical follow up was 61 months (mean 64, range 6-233). Permanent morbidity occurred in 5.9% of cases at last follow-up. Stereotactic radiosurgery is a safe and effective method for treating benign CSM in the medium term to long term.

Risk Factors for Radiation Necrosis in Patients Undergoing Cranial Stereotactic Radiosurgery

Simple Summary

Radiation necrosis is a known complication after stereotactic radiosurgery of intracranial tumors. We evaluated 388 patients who underwent stereotactic radiosurgery at our institution. The most common tumors were metastases (47.2%), followed by vestibular schwannomas (32.2%) and meningiomas (13.4%). 15.7% developed radiation necrosis after a median of 8 months. According to our data, larger tumor diameter (HR 1.065) and higher radiation dose (HR 1.302) were associated with an increased risk of radiation necrosis independently of tumor type. Advanced age was shown to be a risk factor for radiation necrosis only in cases with metastasis (HR 1.066). The data from this study suggest that the development of radiation necrosis is dependent on size and dose, not on the type of the neoplasm.

Abstract

Purpose: single-staged stereotactic radiosurgery (SRS) is an established part of the multimodal treatment in neuro-oncology. Radiation necrosis after high-dose irradiation is a known complication, but there is a lack of evidence about the risk factors. The aim of this study was to evaluate possible risk factors for radiation necrosis in patients undergoing radiosurgery. Methods: patients treated with radiosurgery between January 2004 and November 2020 were retrospectively analyzed. The clinical data, imaging and medication were gathered from electronic patient records. The largest diameter of the tumors was measured using MRI scans in T1 weighted imaging with gadolinium and the edema in T2 weighted sequences. The diagnosis of a radiation necrosis was established analyzing imaging criteria combined with clinical course or pathologically confirmed by subsequent surgical intervention. Patients developing radiation necrosis detected after SRS were compared to patients without evidence of an overshooting irradiation reaction. Results: 388 patients were included retrospectively, 61 (15.7%) of whom developed a radiation necrosis. Median follow-up was 24 (6–62) months with a radiation necrosis after 8 (6–12) months. The most frequent tumors were metastases in 47.2% of the cases, followed by acoustic neuromas in 32.2% and meningiomas in 13.4%. Seventy-three (18.9%) patients already underwent one or more previous radiosurgical procedures for different lesions. The mean largest diameter of the tumors amounted to 16.3 mm (±6.1 mm). The median—80%—isodose administered was 16 (14–25) Gy. Of the radiation necroses, 25 (43.1%) required treatment, in 23 (39.7%) thereof, medical treatment was applied and in 2 (3.4%) cases, debulking surgery was performed. In this study, significantly more radiation necroses arose in patients with higher doses (HR 1.3 [CI 1.2; 1.5], p < 0.001) leading to a risk increment of over 180% between a radiation isodose of 14 and 20 Gy. The maximum diameter was a second significant risk factor (p = 0.028) with an HR of 1065 for every 1 mm increase in multivariate analysis. Conclusion: large diameter and high doses were reliable independent risk factors leading to more frequent radiation necroses, regardless of tumor type in patients undergoing radiosurgery. Alternative therapeutic procedures may be considered in lesions with large volume and an expected high radiation doses due to the increased risk of developing radiation necrosis.

Reactor-based boron neutron capture therapy for 44 cases of recurrent and refractory high-grade meningiomas with long-term follow-up

BACKGROUND

High-grade meningioma (HGM) is difficult to treat, and recurrent HGM after radiotherapy has an especially poor prognosis. We retrospectively analyzed the cases of 44 consecutive patients with recurrent and refractory HGM who were treated by reactor-based boron neutron capture therapy (BNCT).

METHODS

In 2005-2019, we treated 44 recurrent and refractory HGMs by reactor-based BNCT. We analyzed the patients' tumor shrinkage, overall survival (OS) after initial diagnosis, OS after BNCT, progression-free survival (PFS) post-BNCT, and treatment failure patterns.

RESULTS

The median OS (mOS) after BNCT and mOS after initial diagnosis were 29.6 (95%CI: 16.1-40.4) and 98.4 (95%CI: 68.7-169.4) months, respectively. The median follow-up after BNCT was 26 (6.4-103) months. The grade 2 (20 cases) and 3 (24 cases) post-BNCT mOS values were 44.4 (95%CI: 27.4-not determined) and 21.55 (10.6-30.6) months, respectively (p=0.0009). Follow-up images were obtained from 36 cases at >3 months post-BNCT; 35 showed tumor shrinkage during the observation period. The post-BNCT median PFS (mPFS) of 36 cases was 13.7 (95%CI: 8.3-28.6) months. The post-BNCT mPFS values in patients with grade 2 and 3 disease were 24.3 (95%CI: 9.8-not determined) and 9.4 (6.3-14.4) months, respectively (p=0.0024). Local recurrence was observed in only 22.2% of cases. These results showed good local tumor control and prolonged survival for recurrent HGM cases.

CONCLUSIONS

Most of these cases had relatively large tumor volumes. The proportion of grade 3 patients was extremely high. Our patients thus seemed to have poor prognoses. Nevertheless, reactor-based BNCT exerted relatively good local control and favorable survival for recurrent and refractory HGMs.

Outcomes of salvage radiation for recurrent world health organization grade II meningiomas: a retrospective cohort study

PURPOSE

The optimal modality of radiation-intensity-modulated radiation therapy (IMRT) or stereotactic radiosurgery (SRS)-in patients with recurrent WHO grade II meningiomas is not well-established. The purpose of this study was to compare progression-free survival (PFS) in patients undergoing salvage IMRT vs SRS. We compared PFS in those with and without history of prior radiation.

METHODS

Forty-two patients with 71 tumor recurrences treated with IMRT or SRS were retrospectively reviewed. Thirty-two salvage treatments were performed on recurrent tumors never treated with prior radiation ('radiation-naïve' cohort), whereas 39 salvage treatments were performed on recurrent tumors previously treated with radiation ('re-treatment cohort').

RESULTS

In the 'radiation-naïve' cohort, 3-year PFS for IMRT and SRS was 68.8% and 60.7%, respectively (p = 0.61). The median tumor volume for patients treated with IMRT was significantly larger than for patients treated with SRS (5.7 vs 2.2 cm³; p = 0.04). The 3-year PFS for salvage IMRT or SRS in the 're-treatment' cohort was 45.4% vs 65.8% in the 'radiation-naïve' cohort (p = 0.008). When analyzing the outcome of multiple re-treatments, median PFS was 47 months for 1^st or 2nd salvage radiation (IMRT or SRS) compared to 16 months for the 3rd or greater salvage radiation treatment (p = 0.003).

CONCLUSION

For salvage radiation of recurrent grade II tumors that are 'radiation-naïve', comparable 3-year PFS rates were found between IMRT and SRS, despite the IMRT group having significantly larger tumors. Salvage radiation overall was less successful in the 're-treatment' cohort compared with the 'radiation-naïve' cohort. Additionally, the effectiveness of radiation significantly declines with successive salvage radiation treatments.

Role of gamma knife radiosurgery for recurrent or residual World Health Organization grade II and III intracranial meningiomas

Background: To analysis the role of gamma knife radiosurgery (GKRS) in treatment of the recurrent or residual World Health Organization (WHO) grade II and III meningiomas.Methods: Between 1995 and 2015, a total of 1163 meningioma patients were treated with GKRS at our single institute; 26 atypical and 6 anaplastic meningiomas were enrolled. The group consisted of 16 men and 16 women with a median age of 59.5 years (range 30-78 years). The median follow-up was 106.5 months (range 40-216 months). All were cases of tumour recurrence except 7 cases of residual lesions. Six patients were given fractionated radiotherapy before the initial course of GKRS (median dose, 56 Gy).Results: The median tumour volume was 3035 mm³ (range 247-11400 mm³). The median prescribed dose to high grade meningioma margin was 14 Gy (range 12-20 Gy,). The median prescribed dose to WHO II and III meningioma were 14 Gy (range 12-18 Gy) and 15 Gy (range 14-20 Gy), respectively. After radiosurgery, local tumour control rate was 50%. Tumour progression was observed in 28 patients; 16 recurrences were local (12 atypical and 4 anaplastic), 8 were marginal (7 atypical and 1 anaplastic), and 4 were distal (3 atypical and 1 anaplastic). Seven patients (21.88%) developed adverse radiation effects after GKRS. WHO grade was strongly associated with survival, with grade II showing a much longer survival (p = 0.01), and a prior history of radiation was associated with decreased survival (p = 0.003). Multivariate analysis showed that WHO grade (hazard ratio, HR: 5.051, p = 0.01) and prior radiation (HR: 5.763, p = 0.004) were independently associated with survival.Conclusions: WHO grade and a prior history of radiation therapy are reliable long-term predictors of overall outcome when treated with GKRS.

Stereotactic radiotherapy for small and very small tumours (≤1 to ≤3 cc): evaluation of the influence of volumetric-modulated arc therapy in comparison to dynamic conformal arc therapy and 3D conformal radiotherapy as a function of flattened and unflattened beam models

Purpose:

The objective of this article is to evaluate the dosimetric efficacy of volumetric modulated arc therapy (VMAT) in comparison to dynamic conformal arc therapy (DCAT) and 3D conformal radiotherapy (3DCRT) for very small volume (≤1 cc) and small volume (≤3 cc) tumours for flattened (FF) and unflattened (FFF) 6 MV beams.

Materials and methods:

A total of 21 patients who were treated with single-fraction stereotactic radiosurgery, using either VMAT, DCAT or 3DCRT, were included in this study. The volume categorisation was seven patients each in <1, 1–2 and 2–3 cc volume. The treatment was planned with 6 MV FF and FFF beams using three different techniques: VMAT/Rapid Arc (RA) (RA_FF and RA_FFF), dynamic conformal arc therapy (DCA_FF and DCA_FFF) and 3DCRT (Static_FF and Static_FFF). Plans were evaluated for target coverage (V100%), conformity index, homogeneity index, dose gradient for 50% dose fall-off, total MU and MU/dose ratio [intensity-modulated radiotherapy (IMRT) factor], normal brain receiving >12 Gy dose, dose to the organ at risk (OAR), beam ON time and dose received by 12 cc of the brain.

Result:

The average target coverage for all plans, all tumour volumes (TVs) and delivery techniques is 96·4 ± 4·5 (range 95·7 ± 6·1–97·5 ± 2·9%). The conformity index averaged over all volume ranges <1, 2, 3 cc> varies between 0·55 ± 0·08 and 0·68 ± 0·04 with minimum and maximum being exhibited by DCA_FFF for 1 cc and Static_FFF/RA_FFF for 3 cc tumours, respectively. Mean IMRT factor averaged over all volume ranges for RA_FF, DCA_FF and Static_FF are 3·5 ± 0·8, 2·0 ± 0·2 and 2·0 ± 0·2, respectively; 50% dose fall-off gradient varies in the range of 0·33–0·42, 0·35–0·40 and 0·38–0·45 for 1, 2 and 3 cc tumours, respectively.

Conclusion:

This study establishes the equivalence between the FF and FFF beam models and different delivery techniques for stereotactic radiosurgery in small TVs in the range of ≤1 to ≤3 cc. Dose conformity, heterogeneity, dose fall-off characteristics and OAR doses show no or very little variation. FFF could offer only limited time advantage due to excess dose rate over an FF beam.

Atypical meningiomas

Meningiomas are the most common primary CNS tumor in adults, representing a third of brain lesions. Their clinical presentation varies greatly, ranging from asymptomatic incidental tumor to fatal tumor. The majority of meningiomas are benign, and gross total resection can achieve very low recurrence rates, with radiation therapy or radiosurgery reserved for recurrences or residual tumor that grows during serial imaging. At the other end of the spectrum, malignant meningiomas, although comprising just 1% of meningiomas, have been recognized to exhibit aggressive behavior that ultimately proves lethal regardless of the extent of resection or whether adjuvant radiation and chemotherapy are utilized. Over the past 2 decades, there has been pathologic recognition of a third type of meningioma known as "atypical," with borderline histologic and clinical features between benign and malignant meningioma. Here we review the clinical features, treatment, and outcomes of atypical meningiomas, with a focus on the impact of extent of resection and radiation therapy on the long-term recurrence rate of completely and incompletely resected atypical meningiomas.

Predictors of Treatment Response and Survival Outcomes in Meningioma Recurrence with Atypical or Anaplastic Histology

BACKGROUND

Recurrence rates for atypical and anaplastic meningiomas range between 9% and 50% after gross total resection and between 36% and 83% after subtotal resection. Optimal treatment of recurrent meningiomas exhibiting atypical/anaplastic histology is complicated because they are often refractory to both surgery and radiation.

OBJECTIVE

To evaluate clinical determinants of recurrence and treatment-specific outcomes in patients with recurrent meningiomas exhibiting atypical/anaplastic histology at our institution.

METHODS

A cohort study was conducted using clinical data of all patients treated for meningiomas with atypical/anaplastic histology at first recurrence between January 1985 and July 2014 at a tertiary cancer center. Predictors of second recurrence were analyzed using competing risks regression models.

RESULTS

Nine hundred eighteen patients with meningioma were screened, of whom 60 (55% female) had recurrent disease with atypical/anaplastic histology at a median age of 58.1 yr at diagnosis. The median follow-up from the time of first recurrence was 36.7 mo, with 32 (53%) patients alive at last follow-up. There was no effect of extent of resection at first recurrence on time to a subsequent recurrence. Inclusion of radiation as primary or adjuvant therapy at first recurrence reduced the risk of progression or subsequent recurrence compared to surgery alone (P = .07).

CONCLUSION

Treatment of recurrent meningiomas with atypical/anaplastic histology remains challenging. Our data, from one of the largest cohorts, suggest better tumor control with the addition of radiation and challenges the importance of extent of resection at first recurrence. A multicenter effort is needed to confirm these findings and propose treatment guidelines.

Linear Accelerator-Based Radiosurgery of Grade I Intracranial Meningiomas

Objective

To determine the local control rate and complication rate in the treatment of grade I intracranial meningiomas.

Methods

A retrospective study was performed of patients with grade I meningioma who received radiosurgery with a dedicated linear accelerator from January 2002 to August 2012 with a minimum follow-up of 2 years. We performed descriptive statistics, logistic regression, and progression-free survival analysis through a Kaplan-Meier curve.

Results

Seventy-five patients with 78 grade I meningiomas received radiosurgery, 39 underwent surgery plus adjuvant radiosurgery, and 36 only radiosurgery. The follow-up median time was 68 months (range, 35–120 months). The tumor control rate was 93%, the 5-year progression-free survival was 92% (95% confidence interval, 77%–98%). Acute toxicity was 2.6%, and grade 1–2 late toxicity was 26.6%. Postradiosurgery edema was the main late morbidity. Age >55 years was the only significant factor for attaining a response >75%. The background of surgery before radiosurgery was the only significant prognostic factor for showing edema (odds ratio 5.78 [95% confidence interval, 2.14–15.64]).

Conclusions

The local control rate attained in our series is similar to that reported in other series worldwide; the acute toxicity rate was low and late toxicity was moderate.

Boron Neutron Capture Therapy for High-Grade Skull-Base Meningioma

Objectives  Boron neutron capture therapy (BNCT) is a nuclear reaction-based tumor cell-selective particle irradiation that occurs when nonradioactive Boron-10 is irradiated with low-energy neutrons to produce high-energy α particles (10B [ n , α] 7Li). Possible complications associated with extended surgical resection render high-grade meningioma (HGM) a challenging pathology and skull-base meningiomas (SBMs) even more challenging. Lately, we have been trying to control HGMs using BNCT. This study aims to elucidate whether the recurrence and outcome of HGMs and SBMs differ based on their location. Design  Retrospective review. Setting  Osaka Medical College Hospital and Kyoto University Research Reactor Institute. Participants  Between 2005 and 2014, 31 patients with recurrent HGM (7 SBMs) were treated with BNCT. Main Outcome Measures  Overall survival and the subgroup analysis by the anatomical tumor location. Results  Positron emission tomography revealed that HGMs exhibited 3.8 times higher boron accumulation than the normal brain. Although tumors displayed transient increases in size in several cases, all lesions were found to decrease during observation. Furthermore, the median survival time of patients with SBMs post-BNCT and after being diagnosed as high-grade were 24.6 and 67.5 months, respectively (vs non-SBMs: 40.4 and 47.5 months). Conclusions  BNCT could be a robust and beneficial therapeutic modality for patients with high-grade SBMs.

Fractionated Gamma Knife Radiosurgery as Initial Treatment for Large Skull Base Meningioma

We present our experience on the hypofractionated Gamma Knife radiosurgery (FGKS) for large skull base meningioma as an initial treatment. We retrospectively reviewed 23 patients with large skull base meningioma ≥10 cm³ who underwent FGKS as the initial treatment option. The mean volume of tumors prior to radiosurgery was 21.2±15.63 cm³ (range, 10.09~71.42). The median total margin dose and marginal dose per fraction were 18 Gy (range, 15~20) and 6 Gy (range, 5~6), respectively. Patients underwent three or four fractionations in consecutive days with the same Leksell® frame. The mean follow-up duration was 38 months (range, 17~78). There was no mortality. At the last follow-up, the tumor volume was stationary in 15 patients (65.2%) and had decreased in 8 patients (34.8%). Six patients who had cranial neuropathy at the time of FGKS showed improvement at the last clinical follow-up. Following FGKS, 4 patients (17%) had new cranial neuropathy. The trigeminal neuropathy was the most common and all were transient. The mean Karnofsky Performance Status score at pre-FGKS and the last clinical follow-up was 97.0±10.4 points (median, 100) and 98.6±6.9 (median, 100) points, respectively. FGKS has showed satisfactory tumor control with functional preservation for large skull base meningiomas. Further prospective studies of large cohorts with long term follow-up are required to clarify the efficacy in the tumor control and functional outcome as well as radiation toxicity.

Impact of radiotherapy in atypical meningioma recurrence: literature review

Evaluate whether radiotherapy (RT) after the neurosurgical treatment of atypical meningiomas (AM) has an impact on the reduction rate of recurrence. A Medline search through October 2017 using "atypical meningioma" returned 1277 papers for initial review. Inclusion criteria were as follows. We analyzed the database and included articles in which the anatomic pathological classification of atypical meningiomas was in accordance with WHO 2007 or WHO 2016 criteria, patients > 18 years of age, and there was postoperative external beam radiation to the tumor bed. Exclusion criteria were WHO grade I or III meningioma, patients who underwent whole-brain radiation, RT used as salvage therapy for recurrence, palliative dose of RT (< 45 Gy), recurrent AMs, and multiple AMs. Papers reporting outcomes in which atypical and anaplastic meningiomas were analyzed together were rejected, as were papers with small samples that may compromise evaluation. After filtering our initial selection, only 17 papers were selected. After reviewing the seventeen articles including a total of 1761 patients (972 female and 799 male; 1.21 female/1.0 male), the difference in proportion of tumor recurrence between patients with and without radiotherapy after neurosurgical procedure was 1.0448, 95% CI [0.8318 to 1.3125], p value = 0.7062. On the basis of this review, there is no evidence to suggest that RT decreases the rate of recurrence in patients with atypical meningiomas.

Analysis the causes of radiosurgical failure in intracranial meningiomas treated with radiosurgery

OBJECTIVES

Surgical resection is a primary indication for intracranial meningioma. Radiosurgery is also an excellent treatment modality for postoperative residual tumors, or tumors in high-risk locations, such as the skull base. Despite multimodality treatments, there are some cases in which radiosurgery fails and surgical resection or re-radiosurgery is required. However, there has not been a comprehensive study focusing on the causes of secondary treatment for local recurrence or a new mass that develops outside the target area after radiosurgery. Hence, we analyzed the causes of radiosurgical failure in patients with meningioma.

METHODS

From 2000 to 2015, we retrospectively reviewed 1086 patients who underwent gamma knife radiosurgery (GKRS) for intracranial meningioma at the Asan Medical Center. Multiple meningiomas or tumors with a volume greater than 7000mm³ were excluded. All patients had a minimum follow-up of 12 months. Finally, 771 patients were enrolled in this study. Clinical symptoms and brain MRI findings were assessed by neurosurgeons. When the tumor size increased and was accompanied by newly developed neurological symptoms, further management was considered (e.g. microsurgical resection and stereotactic radiosurgery). Histological analyses of the resected tumors were performed by neuropathologists.

RESULTS

Among the 771 patients, tumor growth was observed in 60 patients (7.78%). Seven patients showed transient tumor growth after GKRS. These patients have been under close observation without any further treatment. Thirty patients (3.89%) underwent re-radiosurgery for tumor control. Another 23 patients underwent procedures other than re-radiosurgery; 8 underwent microsurgical resection, 3 underwent cyber knife radiosurgery (CKRS), 1 underwent radiation therapy, and 8 were closely followed-up. Three patients visited other clinics or were lost to follow-up. Of the remaining 30 patients, 22 (group 1) underwent microsurgical resection prior to their initial course of GKRS and the other 8 (group 2) were treated only with re-radiosurgery. In group 1, recurrence rates after radiosurgery were 2.47% (n=19) and 0.39% (n=3) for local and distant recurrence, respectively. In group 2, recurrence rates after radiosurgery were 0.52% (n=4) and 0.52% (n=4) for local and distant recurrence, respectively. An analysis was performed to determine the factors that may result in differences between the two groups. Of the many variables, local recurrence (p=0.0331, Fisher's exact test) was the only significant factor.

CONCLUSION

We analyzed the causes of radiosurgical failure in meningioma patients and observed that microsurgery before radiosurgery was significantly associated with a high local recurrence rate compared with primary radiosurgery. Furthermore, the percentage of local recurrence cases that required secondary radiosurgery was as low as 2.98%. This result is comparable with that of microsurgical resection, which is the mainstay of treatment for meningioma.

Analysis of the results of recurrent intracranial meningiomas treated with re-radiosurgery

OBJECTS

Meningioma is the most common intracranial neoplasm, comprising approximately 30% of all primary intracranial tumors (Claus et al., 2005) [1]. Treatment options include observation, microsurgical resection, stereotactic radiosurgery (SRS), and whole brain radiation therapy (WBRT). Gamma knife radiosurgery (GKRS) is a very effective treatment for intracranial meningiomas; previous studies showed the tumor control rate at 5-10 years of follow-up as 84.3%-100% in all cases (Feigl et al., 2005; Linskey et al., 2005; Malik et al., 2005; Aichholzer et al., 2000; Hakim et al., 1998; Chang and Adler 1997; Lunsford, 1994; Ganz et al., 1993) [2-9]. Many studies have discussed issues like optimal dose, conformal configurations, and adverse effects to improve the treatment result with GKRS (Malik et al., 2005; Kenai et al., 2005; Rowe et al., 2004; Shrieve et al., 2004) [4,10-12]. There are some cases in which the radiosurgery result is unfavorable and perhaps further treatment is needed. In these cases, re-radiosurgery can be an option. However, there have not been comprehensive studies discussing the issues of re-radiosurgery. Therefore, we analyzed the result of re-radiosurgery for recurrent meningiomas and their impact on clinical outcomes.

METHODS

From 1995 to 2015, we retrospectively reviewed 1163 patients who underwent GKRS for intracranial meningioma at the Asan Medical Center. Patients with multiple meningiomas or a follow-up with a period of less than a year were excluded from this study. Finally, 865 patients were enrolled in this study. Clinical symptoms and brain magnetic resonance imaging (MRI) scans were assessed by neurosurgeons. When tumor size increased together with newly developed neurologic symptoms, further management, such as microsurgical resection or SRS, was considered. Histologic analysis of the resected tumors was performed by neuropathologists. Clinical data, including patient's sex, age, and tumor locations were recorded. Treatment data included tumor volume, tumor grade, radiation dose, and presence of edema. Final outcome data including follow-up period, time to progression, interval between first and second radiosurgery courses and interval between microsurgery and radiosurgery were obtained.

RESULTS

Among 865 patients, tumor recurrence was found in 63 patients (7.28%). Seven patients showed transient tumor growth after GKRS. These patients have been under close observation without any further treatments. Fifty-six patients (6.47%) showed permanent tumor growth on follow-up MRI. Thirty-three patients from this group underwent repeated radiosurgery owing to tumor growth, resulting in a re-irradiation rate of 3.82% at our radiosurgery center. The other 23 patients were treated using methods other than re-radiosurgery. Among the 33 patients, 25 underwent microsurgical resection prior to their initial course of GKRS, and the other 8 were treated with re-radiosurgery only. An analysis was performed to determine factors that may have a role in treatment results. Of the many variables, tumor grade (p=0.004, Fisher's exact test) was the only significant factor for progression-free survival (PFS). Thirteen patients with unbiopsied or benign meningioma showed stable tumor size, while there was tumor growth in 8 patients. Among high-grade meningioma patients, 3 and 9 showed stable disease and tumor growth, respectively. As a result of re-radiosurgery, 11 out of 17 patients showed tumor growth and needed further treatments; this involved a third GKRS for 4 patients, microsurgical resection for 6 patients, and cyber knife radiosurgery (CKRS) for 1 patient. Four patients from this group were also treated with WBRT.

CONCLUSION

We analyzed the results of re-radiosurgery for recurrent meningiomas and observed that World Health Organization (WHO) grade II and III was significantly associated with a lower PFS rate compared with low-grade meningiomas (p=0.004). Conversely, patients with benign meningioma or unbiopsied tumors had much better results. Hence, re-radiosurgery is recommended for patients with unknown or benign meningiomas if their first GKRS result is unsatisfactory. However, re-radiosurgery should be considered carefully for recurrent high-grade tumors. Owing to the small number of recurrent meningioma patients treated with re-radiosurgery, further studies are required to delineate the role of this treatment.

A case of an anaplastic meningioma metastasizing to the mediastinal lymph nodes

CONTEXT

Grade II and III (World Health Organization classification) meningiomas rarely develop in the spinal cord. However, we experienced a case with an anaplastic meningioma that developed in the spinal cord at the cervicothoracic junction and metastasized to the mediastinal lymph nodes. No such cases have previously been reported.

FINDINGS

The patient was a 68-year-old man who developed back pain that did not affect his daily living. He developed left lower limb paralysis, and was admitted after magnetic resonance imaging (MRI) revealed an intramedullary tumor at the level of cervical vertebra 7 and thoracic vertebra 1. Positron emission tomography revealed tracer uptake in the intramedullary tumor and the mediastinal lymph nodes, suggesting a metastatic spinal cord tumor or malignant lymphoma. A lymph node biopsy was then performed. Although the tumor was highly malignant, its primary site was not identified. Detailed examinations by several other departments revealed no abnormalities. On hospital day 30, his left lower limb paralysis deteriorated, and MRI revealed that the tumor had grown. Thus, laminaplasty, laminectomy, and tumor resection were performed. The tumor was an anaplastic meningioma that resembled mediastinal lymph node tissue, and other tumor lesions were not found. These findings suggested that an anaplastic meningioma had metastasized to the mediastinal lymph nodes. The patient did not respond to radiotherapy, and he was transferred to another hospital.

CONCLUSION

In cases of intramedullary spinal tumors with metastasis without other potential primary tumor lesions, early diagnosis and treatment should be performed while considering anaplastic meningioma.

Gamma Knife Radiosurgery for Atypical and Anaplastic Meningiomas

BACKGROUND

Atypical and anaplastic meningiomas have much higher recurrence rates after surgical resection compared with benign meningiomas, but the role of adjuvant radiosurgery remains unclear. This study was undertaken to evaluate the outcomes of gamma knife radiosurgery for patients with atypical and anaplastic meningiomas.

METHODS

In this retrospective analysis of a prospectively maintained database, 46 patients with histologically proven atypical or anaplastic meningiomas by current World Health Organization (WHO) criteria underwent postoperative Gamma Knife radiosurgery between 1993 and 2013. The median follow-up period was 32.6 months. The median tumor volume and margin dose were 11.7 mL (range, 2-53 mL) and 13.1 Gy (range, 12.0-16.5 Gy), respectively.

RESULTS

Local control at 3 and 5 years was 50.6% and 32.1%, respectively. Gender (P = 0.013) and marginal dose less than or equal to 13 Gy (P = 0.049) were associated with the local control. The 3- and 5-year overall survival for patients with WHO grade II was 97.1% and 88.3%, respectively, compared with 66.7% and 66.7% for patients with WHO grade III meningiomas. Radiation therapy before Gamma Knife radiosurgery (GKRS; P = 0.018) and tumor grade (P = 0.019) were the factors associated with a worse overall survival rate. Fourteen patients (30.4%) developed adverse radiation effects after GKRS treatment, and all were Radiation Therapy Oncology Group grade I.

CONCLUSIONS

Postoperative GKRS treatment for patients with atypical and anaplastic meningioma is challenging. More aggressive treatment, including of safely maximizing the extent of surgical resection and using a higher margin dose (>13Gy), should be applied to achieve better local control.

Stereotactic LINAC radiosurgery for the treatment of typical intracranial meningiomas. Efficacy and safety after a follow-up of over 12 years

PURPOSE

The efficacy and safety of stereotactic radiosurgery (SRS) for treatment of intracranial meningiomas has been demonstrated in numerous studies with short- and intermediate-term follow-up. In this retrospective single-center study, we present long-term outcomes of SRS performed with a linear accelerator (LINAC) for typical intracranial meningiomas.

PATIENTS AND METHODS

Between August 1990 and December 2007, 148 patients with 168 typical intracranial meningiomas were treated with stereotactic LINAC-SRS, either as primary treatment or after microsurgical resection. A median tumor surface dose of 12 Gy (range 7-20 Gy) and a median maximum dose of 24.1 Gy (range 11.3-58.6 Gy) was applied. The median target volume was 4.7 ml (range 0.2-32.8 ml, SD ± 4.8 ml).

RESULTS

Overall mean radiological follow-up was 12.6 years. Tumor shrinkage was seen in 75 (44.6 %) and stable disease in 85 (50.6 %) cases. Eight of 168 meningiomas (4.8 %) showed local tumor progression. The tumor control rate (TCR) after 5, 10, and 15 years was 93.6 % at each time point, and the progression-free survival (PSF) rates were 92, 89, and 89 %, respectively. The neurological symptoms existing prior to LINAC-SRS improved in 77 patients (59.7 %), remained unchanged in 42 (32.6 %), and deteriorated in 10 (7.8 %) patients.

CONCLUSION

Our study emphasizes the efficacy of LINAC-SRS for de novo, residual and recurrent typical intracranial meningiomas. A high long-term local TCR with a low morbidity rate could be achieved. LINAC-SRS should thus be considered as a primary treatment option, as one arm of a combined treatment approach for incompletely resected meningiomas, or as a salvage therapy for recurrences.

Regaining vision from no perception of light after radiotherapy for a case of suprasellar meningioma

Meningiomas are tumours of the arachnoid cap cells. Usually they are referred to according to their location. They are primarily treated with surgery. They tend to recur following surgery. Suprasellar meningiomas frequently present with visual disturbances. Our patient is a case of recurrent suprasellar meningioma. The visual acuity in one eye was No Perception of Light(NPL). From NPL, the visual acuity improved to 6/12 in six months after High Precision Irradiation (HPI). This case emphasizes the importance and the need for aggressive management. It also shows the use of radiotherapy techniques used in synergy to produce the necessary results.

Is There a Tumor Volume Threshold for Postradiosurgical Symptoms? A Single-Institution Analysis

BACKGROUND:

Single-fraction radiosurgery may carry a higher risk of symptomatic peritumoral edema than conventionally fractionated radiotherapy, with a reported incidence of 2.5% to 37%. Previous research has shown that larger tumor volume and margin dose &gt;14 Gy are associated with increased risk of toxicity. Parasagittal location has been associated with toxicity in some studies, but not in others.

OBJECTIVE:

To determine risk factors for and patterns of postradiosurgical symptoms (PRS).

METHODS:

This single-institution retrospective chart review included 282 stereotactic radiosurgery procedures for an intracranial meningioma from January 1999 to March 2011. PRS were assessed by using the Common Terminology Criteria for Adverse Events (Version 4.0). Statistical analyses were conducted by using the 194 procedures for which treatment plans were available.

RESULTS:

PRS were observed after 65 procedures (23%); 35 (12%) were grade 2 or higher. Posttreatment edema occurred in 21% of grade I PRS, 68% of grade II PRS, and 71% of grade III PRS. Tumor volume ≥7.1 cc (adjusted hazards ratio = 4.9, P = .02), prior external beam radiotherapy (adjusted hazards ratio = 2.6, P = .03), and histological grade (P = .005) predicted PRS. On multivariate analysis, parasagittal location was not predictive of PRS, although skull base location predicted a lower risk of symptomatic posttreatment edema (adjusted hazards ratio = 0.133, P = .02).

CONCLUSION:

In our series, prior external beam radiotherapy, tumor volume, and tumor grade are risk factors for PRS, while pretreatment edema approached statistical significance. Peritumoral edema is the predominant mechanism of significant PRS, and skull base tumors have a lower risk of posttreatment edema.

Novel therapies for meningiomas

Although advances in surgery, radiation therapy and stereotactic radiosurgery have significantly improved the treatment of meningiomas, there remains an important subset of patients who remain refractory to conventional therapy. Treatment with chemotherapeutic agents such as hydroxyurea and alpha-interferon has provided minimal benefit. In this review, the role of newly emerging novel therapies for meningiomas, with a focus on targeted molecular agents, will be discussed.

Patterns of recurrence after stereotactic radiosurgery for treatment of meningiomas

Object

The purpose of this study was to evaluate patterns of failure after stereotactic radiosurgery (SRS) for meningiomas and factors that may influence these outcomes.

Methods

Based on a retrospective chart review, 279 patients were treated with SRS for meningiomas between January 1999 and March 2011 at Wake Forest Baptist Health. Disease progression was determined using serial imaging, with a minimum follow-up of 6 months (median 34.2 months).

Results

The median margin dose was 12.0 Gy (range 8.8–20 Gy). Local control rates for WHO Grade I tumors were 96.6%, 84.4%, and 75.7% at 1, 3, and 5 years, respectively. WHO Grade II and III tumors had local control rates of 72.3%, 57.7%, and 52.9% at 1, 3, and 5 years, respectively. Tumors without pathological grading had local control rates of 98.7%, 97.6%, and 94.2% at 1, 3, and 5 years, respectively. Of the local recurrences, 63.1% were classified as marginal (within 2 cm of treatment field). The 1-, 3-, and 5-year rates of distant failure were 6.5%, 10.3%, and 16.6%, respectively, for Grade I tumors and 11.4%, 17.2%, and 22.4%, respectively, for Grade II/III tumors. Tumors without pathological grading had distant failure rates of 0.7%, 3.2%, and 6.5% at 1, 3, and 5 years, respectively. Wilcoxon analysis revealed that multifocal disease (p < 0.001) and high-grade histology (WHO Grade II or III; p < 0.001) were significant predictors of local recurrence. Additionally, male sex was a significant predictor of distant recurrence (p = 0.04). Multivariate analysis also showed that doses greater than or equal to 12 Gy were associated with improved local control (p = 0.015).

Conclusions

In this patient series, 12 Gy was the minimum sufficient margin dose for the treatment of meningiomas. Male sex is a risk factor for distant failure, whereas high-grade histology and multifocal disease are risk factors for local failure.

The role of radiosurgery in the management of WHO Grade II and III intracranial meningiomas

Object

WHO Grade II and III intracranial meningiomas are uncommon, but they portend a significantly worse prognosis than their benign Grade I counterparts. The mainstay of current management is resection to obtain cytoreduction and histological tissue diagnosis. The timing and benefit of postoperative fractionated external beam radiation therapy and stereotactic radiosurgery remain controversial. The authors review the stereotactic radiosurgery outcomes for Grade II and III meningiomas.

Methods

A comprehensive literature search was performed using PubMed to identify all radiosurgery series reporting the treatment outcomes for Grade II and III meningiomas. Case reports and case series involving fewer than 10 patients were excluded.

Results

From 1998 to 2013, 19 radiosurgery series were published in which 647 Grade II and III meningiomas were treated. Median tumor volumes were 2.2–14.6 cm3. The median margin doses were 14–21 Gy, although generally the margin doses for Grade II meningiomas were 16–20 Gy and the margin doses for Grade III meningiomas were 18–22 Gy. The median 5-year PFS was 59% for Grade II tumors and 13% for Grade III tumors, which may have been affected by patient age, prior radiation therapy, tumor volume, and radiosurgical dose and timing. The median complication rate following radiosurgery was 8%.

Conclusions

The current data for radiosurgery suggest that it has a role in the management of residual or recurrent Grade II and III meningiomas. However, better studies are needed to fully define this role. Due to the relatively low prevalence of these tumors, it is unlikely that prospective studies will be feasible. As such, well-designed retrospective analyses may improve our understanding of the effect of radiosurgery on tumor recurrence and patient survival and the incidence and impact of treatment-induced complications.

Controversies in radiotherapy for meningioma

Meningiomas are the most common primary intracranial tumour. Although external beam radiotherapy and radiosurgery are well-established treatments, affording local control rates of 85-95% at 10 years, the evidence base is mainly limited to single institution case series. This has resulted in inconsistent practices. It is generally agreed that radiotherapy is an established primary therapy in patients requiring treatment for surgically inaccessible disease and postoperatively for grade 3 tumours. Controversy exists surrounding whether radiotherapy should be upfront or reserved for progression for incompletely excised and grade 2 tumours. External beam radiotherapy and radiosurgery have not been directly compared, but seem to offer comparable rates of control for benign disease. Target volume definition remains contentious, including the inclusion of hyperostotic bone, dural tail and surrounding brain, but pathological studies are shedding some light. Most agree that doses around 50-54 Gy are appropriate for benign meningiomas and ongoing European Organization for Research and Treatment of Cancer and Radiation Therapy Oncology Group studies are evaluating dose escalation for higher risk disease. Here we address the 'who, when and how' of radiotherapy for meningioma.

Boron neutron capture therapy for recurrent high-grade meningiomas

OBJECT

Similar to glioblastomas, high-grade meningiomas are difficult pathologies to control. In this study, the authors used boron neutron capture therapy (BNCT), a tumor-selective intensive particle radiation modality, to treat high-grade meningioma.

METHODS

From June 2005 to September 2011, BNCT was applied 28 times in 20 cases of recurrent high-grade meningioma. All patients had previously undergone intensive treatments such as repetitive surgeries and multiple sessions of radiation therapy. Fluorine-18-labeled boronophenylalanine ((18)F-BPA) PET was performed before BNCT in 19 of the 20 cases; BPA is itself a therapeutic compound. Compound uptake, tumor shrinkage, long-term control rate including survival time, and failure pattern of the treated patients were all evaluated.

RESULTS

Eighteen of 19 cases studied using (18)F-BPA PET showed good BPA uptake, with ratios of tumor to normal brain greater than 2.7. These ratios indicated the likely effects of BNCT prior to neutron irradiation. The original tumor sizes were between 4.3 cm(3) and 109 cm(3). A mean tumor volume reduction of 64.5% was obtained after BNCT within just 2 months. The median follow-up duration was 13 months. Six patients are still alive; at present, the median survival times after BNCT and diagnosis are 14.1 months (95% CI 8.6-40.4 months) and 45.7 months (95% CI 32.4-70.7 months), respectively. Clinical symptoms before BNCT, such as hemiparesis and facial pain, were improved after BNCT in symptomatic cases. Systemic metastasis, intracranial distant recurrence outside the radiation field, CSF dissemination, and local tumor progression were observed in 6, 7, 3, and 3 cases, respectively, during the clinical course. Apparent pseudoprogression was observed in at least 3 cases. Symptomatic radiation injuries occurred in 6 cases, and were controllable in all but 1 case.

CONCLUSIONS

Boron neutron capture therapy may be especially effective in cases of high-grade meningioma.

Gamma knife stereotactic radiosurgery for atypical and malignant meningiomas

BACKGROUND

Non-benign meningioma has a known trend to recur repeatedly. The results of Gamma Knife stereotactic radiosurgery (GKS) for recurrent or residual atypical and malignant meningiomas are reported.

METHODS

Thirty patients (13 men, 17 women) with World Health Organization (WHO) grade II (24 cases) or grade III (6 cases) intracranial meningiomas underwent GKS. Their age varied from 30 to 86 years (mean 64 years). Before GKS, the tumor was surgically resected in all patients, and 11 of them also underwent conventional external beam radiation therapy, LINAC-based stereotactic radiotherapy (SRT), or intensity-modulated radiation therapy.

FINDINGS

Of the 30 patients, 23 were followed after the initial GKS for a median period of 28 months (range 2-135 months). Local tumor control after treatment was 74 % at 1 year, 52 % at 2 years, and 34 % at 3 years. A total of 15 patients underwent repeat GKS (one to nine times) because of local or distant intracranial tumor progression, seven were subjected to surgical re-resection of the neoplasm, and four had additional SRT. At the time of the last follow-up, 21 patients were alive, and 2 had died. One of the latter expired because of brain tumor progression at 91 months after the initial GKS, and the other patient died from lung cancer.

CONCLUSIONS

Although atypical and malignant meningiomas have a trend to recur repeatedly, aggressive tumor management with repeat GKS at the time of progression can provide long survival in these patients.

Long-term tumor control of benign intracranial meningiomas after radiosurgery in a series of 4565 patients

BACKGROUND

Radiosurgery is the main alternative to microsurgical resection for benign meningiomas.

OBJECTIVE

To assess the long-term efficacy and safety of radiosurgery for meningiomas with respect to tumor growth and prevention of associated neurological deterioration. Medium- to long-term outcomes have been widely reported, but no large multicenter series with long-term follow-up have been published.

METHODS

From 15 participating centers, we performed a retrospective observational analysis of 4565 consecutive patients harboring 5300 benign meningiomas. All were treated with Gamma Knife radiosurgery at least 5 years before assessment for this study. Clinical and imaging data were retrieved from each center and uniformly entered into a database by 1 author (A.S.).

RESULTS

Median tumor volume was 4.8 cm³, and median dose to tumor margin was 14 Gy. All tumors with imaging follow-up < 24 months were excluded. Detailed results from 3768 meningiomas (71%) were analyzed. Median imaging follow-up was 63 months. The volume of treated tumors decreased in 2187 lesions (58%), remained unchanged in 1300 lesions (34.5%), and increased in 281 lesions (7.5%), giving a control rate of 92.5%. Only 84 (2.2%) enlarging tumors required further treatment. Five- and 10-year progression-free survival rates were 95.2% and 88.6%, respectively. Tumor control was higher for imaging defined tumors vs grade I meningiomas (P < .001), for female vs male patients (P < .001), for sporadic vs multiple meningiomas (P < .001), and for skull base vs convexity tumors (P < .001). Permanent morbidity rate was 6.6% at the last follow-up.

CONCLUSION

Radiosurgery is a safe and effective method for treating benign meningiomas even in the medium to long term.

Single-Fraction Radiosurgery of Benign Intracranial Meningiomas

BACKGROUND:

Stereotactic radiosurgery (SRS) of benign intracranial meningiomas is an accepted management option for well-selected patients.

OBJECTIVE:

To analyze patients who had single-fraction SRS for benign intracranial meningiomas to determine factors associated with tumor control and neurologic complications.

METHODS:

Retrospective review was performed of 416 patients (304 women/112 men) who had single-fraction SRS for imaging defined (n = 252) or confirmed World Health Organization grade I (n = 164) meningiomas from 1990 to 2008. Excluded were patients with radiation-induced tumors, multiple meningiomas, neurofibromatosis type 2, and previous or concurrent radiotherapy. The majority of tumors (n = 337; 81%) involved the cranial base or tentorium. The median tumor volume was 7.3 cm3; the median tumor margin dose was 16 Gy. The median follow-up was 60 months.

RESULTS:

The disease-specific survival rate was 97% at 5 years and 94% at 10 years. The 5- and 10-year local tumor control rate was 96% and 89%, respectively. Male sex (hazard ratio [HR]: 2.5, P = .03), previous surgery (HR: 6.9, P = .002) and patients with tumors located in the parasagittal/falx/convexity regions (HR: 2.8, P = .02) were negative risk factors for local tumor control. In 45 patients (11%) permanent radiation-related complications developed at a median of 9 months after SRS. The 1- and 5-year radiation-related complication rate was 6% and 11%, respectively. Risk factors for permanent radiation-related complication rate were increasing tumor volume (HR: 1.05, P = .008) and patients with tumors of the parasagittal/falx/convexity regions (HR: 3.0, P = .005).

CONCLUSION:

Single-fraction SRS at the studied dose range provided a high rate of tumor control for patients with benign intracranial meningiomas. Patients with small volume, nonoperated cranial base or tentorial meningiomas had the best outcomes after single-fraction SRS.

μMLC-LINAC radiosurgery for intracranial meningiomas of complex shape

BACKGROUND

We present the long-term results of a consecutive series of patients with meningiomas treated by LINAC-radiosurgery using the micro-multi-leaf collimator technique (μMLC).

METHODS

Between May 2001 and July 2009, 78 patients (m: f = 024:54; median age, 56.8 years; range, 20.1-81 years) with 87 intracranial meningiomas (78 WHO I, seven WHO II, two WHO III) were treated with μMLC-LINAC radiosurgery at our institution, either as a primary or salvage treatment following one or more microsurgical procedures. Fifty-eight of 87 tumors (66.7%) were located in the skull base. The remaining 29 meningiomas (33.3%) were located in the convexity of the brain. The median tumor volume was 4.8 ml (range, 0.2-18.3 ml). The median tumor surface dose, maximal dose, and therapeutic isodose were 12 Gy, 16 Gy, and 75%, respectively.

RESULTS

For retrospective evaluation, we included 70 patients (78 tumors) with a minimum radiological follow-up of 24 months. After a median follow-up of 79.7 months (range, 24.2-109.1 months), 24 patients (34.3%) improved in their clinical status (paresis of N. abducens 18/48, facial paresis 4/8, and hemiparesis 2/9), 41 patients remained stable (58.6%), three patients had treatment-related temporary complaints (4.3%); two patients developed vertigo, and one had a left-sided hemihypesthesia. All complaints recovered completely after steroid medication within 2 weeks. Two patients (2.8%) developed permanent trigeminal neuralgia. Follow-up MR images showed a partial remission in 21 tumors (26.9%) and a stable tumor size in 55 cases (70.5%). Two patients with high-grade meningiomas showed a tumor progression (one WHO II and one WHO III meningioma). At the end of follow-up (July 2010), the actuarial 5- and 9-year progression-free survival after radiosurgery were 98 and 96%, respectively. There was no treatment-related mortality.

CONCLUSIONS

LINAC radiosurgery using a micro multi-leaf collimator for complex shaped intracranial meningiomas is effective yielding a high local tumor control, whereas the treatment-related morbidity remains low.

Patterns of failure after treatment of atypical meningioma with gamma knife radiosurgery

Atypical meningiomas have poor local control with emerging literature indicating the use of radiosurgery in treatment. The purpose of this study was to evaluate clinical outcomes including local control and failure pattern after Gamma Knife radiosurgery (GKRS) and factors that may affect these outcomes. Between 1999 and 2008, 24 patients were treated with GKRS as either primary or salvage treatment for pathologically proven atypical meningiomas. Treatment failures were determined by serial magnetic resonance imaging. A median marginal dose of 14 Gy was used (range 10.5-18 Gy). Overall local control rates at 1, 2, and 5 years were 75, 51, and 44%, respectively. With median follow-up time of 42.5 months, 14 of 24 patients experienced a treatment failure at time of last follow-up. Eight recurrences were in-field, four were marginal failures, and two were distant failures. Wilcoxon analysis revealed that the conformality index (CI) was a significant predictor of local recurrence (P = 0.04). CI did not predict for distant recurrences (P = 0.16). On multivariate analysis evaluating factors predicting progression free survival, dose >14 Gy was found to be statistically significant (P = 0.01). There appears to be a dose response using GKRS beyond 14 Gy but given the suboptimal local control rates in this study, higher doses may still be needed to obtain better local control.

Cyberknife stereotactic radiosurgery for treatment of atypical (WHO grade II) cranial meningiomas

BACKGROUND

The optimal management of subtotally resected atypical meningiomas is unknown.

OBJECTIVE

To perform a retrospective review of patients with residual or recurrent atypical meningiomas treated with stereotactic radiosurgery (SRS).

METHODS

Twenty-five patients were treated, either immediately after surgery (n = 15) or at the time of radiographic progression or treatment failure (n = 10). SRS was delivered to with a median marginal dose of 22 Gy (range, 16-30) in 1 to 4 fractions (median, 1), targeting a median tumor volume of 5.3 cm³ (range, 0.3-26.0).

RESULTS

With a median follow-up time of 28 months (range, 3-67), the 12-, 24-, and 36-month actuarial local and regional control rates for all patients were 94%, 94%, 74%, and 90%, 90%, 62%, respectively. There were 2 cases of radiation toxicity. On univariate analysis, the number of recurrences before SRS (P = .046), late SRS (ie, waiting until tumor progression to initiate treatment) (P = .03), and age at treatment ≥ 60 years (P = .01) were significant predictors of recurrence. Of the 20 radiation-naïve patients, 2 patients failed with the targeted lesion and 3 elsewhere in the resection bed, resulting in 12-, 24- and 36-month actuarial local and regional control rates of 100%, 100%, 73% and 93%, 93%, 75%, respectively. The overall locoregional control rates at 12, 24, and 36 months were 93%, 93%, and 54%, respectively.

CONCLUSION

Irradiation of the entire postoperative tumor bed may not be necessary for the majority of patients with subtotally resected atypical meningiomas. Patients in this series achieved outcomes comparable to that of historical control rates for larger volume, conventionally fractionated radiotherapy.

Proton stereotactic radiosurgery for the treatment of benign meningiomas

PURPOSE

Given the excellent prognosis for patients with benign meningiomas, treatment strategies to minimize late effects are important. One strategy is proton radiation therapy (RT), which allows less integral dose to normal tissue and greater homogeneity than photon RT. Here, we report the first series of proton stereotactic radiosurgery (SRS) used for the treatment of meningiomas.

METHODS AND MATERIALS

We identified 50 patients with 51 histologically proven or image-defined, presumed-benign meningiomas treated at our institution between 1996 and 2007. Tumors of <4 cm in diameter and located≥2 mm from the optic apparatus were eligible for treatment. Indications included primary treatment (n=32), residual tumor following surgery (n=8), and recurrent tumor following surgery (n=10). The median dose delivered was 13 Gray radiobiologic equivalent (Gy[RBE]) (range, 10.0-15.5 Gy[RBE]) prescribed to the 90% isodose line.

RESULTS

Median follow-up was 32 months (range, 6-133 months). Magnetic resonance imaging at the most recent follow-up or time of progression revealed 33 meningiomas with stable sizes, 13 meningiomas with decreased size, and 5 meningiomas with increased size. The 3-year actuarial tumor control rate was 94% (95% confidence interval, 77%-98%). Symptoms were improved in 47% (16/34) of patients, unchanged in 44% (15/34) of patients, and worse in 9% (3/34) of patients. The rate of potential permanent adverse effects after SRS was 5.9% (3/51 patients).

CONCLUSIONS

Proton SRS is an effective therapy for small benign meningiomas, with a potentially lower rate of long-term treatment-related morbidity. Longer follow-up is needed to assess durability of tumor control and late effects.

Tumor shrinkage assessed by volumetric MRI in the long-term follow-up after stereotactic radiotherapy of meningiomas

PURPOSE

To evaluate tumor volume reduction in the follow-up of meningiomas after fractionated stereotactic radiotherapy (FSRT) or linac radiosurgery (RS) by using magnetic resonance imaging (MRI).

PATIENTS AND METHODS

In 59 patients with skull base meningiomas, gross tumor volume (GTV) was outlined on contrast-enhanced MRI before and median 50 months (range 11-92 months) after stereotactic radiotherapy. MRI was performed as an axial three-dimensional gradient-echo T1-weighted sequence at 1.6 mm slice thickness without gap (3D-MRI). Results were compared to the reports of diagnostic findings.

RESULTS

Mean tumor size of all 59 meningiomas was 13.9 ml (0.8-62.9 ml) before treatment. There was shrinkage of the treated meningiomas in all but one patient. Within a median volumetric follow-up of 50 months (11-95 months), an absolute mean volume reduction of 4 ml (0-18 ml) was seen. The mean relative size reduction compared to the volume before radiotherapy was 27% (0-73%). Shrinkage measured by 3D-MRI was greater at longer time intervals after radiotherapy. The mean size reduction was 17%, 23%, and 30% (at < 24 months, 24-48 months, and 48-72 months).

CONCLUSION

By using 3D-MRI in almost all patients undergoing radiotherapy of a meningioma, tumor shrinkage is detected. The data presented here demonstrate that volumetric assessment from 3D-MRI provides additional information to routinely used radiologic response measurements. After FSRT or RS, a mean size reduction of 25-45% can be expected within 4 years.

En plaque sphenoid wing meningiomas: recurrence factors and surgical strategy in a series of 71 patients

OBJECTIVE

En plaque sphenoid wing meningiomas are complex tumors involving the sphenoid wing, the orbit, and sometimes the cavernous sinus. Complete removal is difficult, so these tumors have high rates of recurrence and postoperative morbidity. The authors report a series of 71 patients with sphenoid wing meningiomas that were managed surgically.

METHODS

The clinical records of 71 consecutive patients undergoing surgery for sphenoid wing meningiomas at Lariboisière Hospital, Paris, were prospectively collected in a database during a 20-year period and analyzed for presenting symptoms, surgical technique, clinical outcome, and follow-up.

RESULTS

Among the 71 patients (mean age, 52. 7 years; range, 12-79 years), 62 were females and 9 were males. The most typical symptoms recorded were proptosis in 61 patients (85.9%), visual impairment in 41 patients (57.7%), and oculomotor paresis in 9 patients (12.7%). Complete removal was achieved in 59 patients (83%). At 6 months of follow-up, magnetic resonance imaging scans revealed residual tumor in 12 patients (9 in the cavernous sinus and 3 around the superior orbital fissure). Mean follow-up was 76.8 months (range, 12-168 months). Tumor recurrence was recorded in 3 of 59 patients (5%) with total macroscopic removal. Among the patients with subtotal resection, tumor progression was observed in 3 of 12 patients (25%; 2 patients with grade III and 1 patient with grade IV resection). Mean time to recurrence was 43.3 months (range, 32-53 months).

CONCLUSION

Surgical management of patients with sphenoid wing meningiomas cannot be uniform; it must be tailored on a case-by-case basis. Successful resection requires extensive intra- and extradural surgery. We recommend optic canal decompression in all patients to ameliorate and/or preserve visual function.

Protecting venous structures during radiosurgery for parasagittal meningiomas

Symptomatic edema is a potential complication of meningioma radiosurgery. Parasagittal meningiomas are at a particular risk for symptomatic edema, suggesting a role for a venous occlusive complication. The authors sought to develop a strategy to optimize CyberKnife stereotactic radiosurgical treatment parameters to reduce the irradiation of the peritumoral venous system. Multislice CT venography with 3D reconstructions was performed and coregistered with thin-section, contrast-enhanced, volumetric MR images. The tumor and critical volumes were contoured on the MR images. Venous anatomical details obtained from the CT venographic study were then exported onto the MR imaging and fused MR imaging-CT study. Target and critical structure volumes and dosimetric parameters obtained with this method were analyzed. The authors found that reducing the irradiation of veins that course along the surface of the meningioma, which may be at risk for radiation-induced occlusion, is feasible in parasagittal meningioma radiosurgery without compromising other treatment parameters including conformality, homogeneity, and target coverage. Long-term follow-up is needed to assess the clinical validity of this treatment strategy.