Postoperative Gamma Knife surgery for benign meningiomas of the cranial base

Re-irradiation for recurrent intracranial meningiomas: Analysis of clinical outcomes and prognostic factors

PURPOSE

Re-irradiation (re-RT) for recurrent intracranial meningiomas is hindered by the limited radiation tolerance of surrounding tissue and the risk of side effects. This study aimed at assessing outcomes, toxicities and prognostic factors in a cohort of patients with recurrent meningiomas re-treated with different RT modalities.

MATERIALS AND METHODS

A multi-institutional database from 8 Italian centers including intracranial recurrent meningioma (RM) patients who underwent re-RT with different modalities (SRS, SRT, PT, EBRT) was collected. Biologically Equivalent Dose in 2 Gy-fractions (EQD2) and Biological Effective Dose (BED) for normal tissue and tumor were estimated for each RT course (α/β = 2 for brain tissue and α/β = 4 for meningioma). Primary outcome was second progression-free survival (s-PFS). Secondary outcomes were overall survival (OS) and treatment-related toxicity. Kaplan-Meier curves and Cox regression models were used for analysis.

RESULTS

Between 2003 and 2021 181 patients (pts) were included. Median age at re-irradiation was 62 (range 20-89) and median Karnofsky Performance Status (KPS) was 90 (range 60-100). 78 pts were identified with WHO grade 1 disease, 65 pts had grade 2 disease and 10 pts had grade 3 disease. 28 pts who had no histologic sampling were grouped with grade 1 patients for further analysis. Seventy-five (41.4 %) patients received SRS, 63 (34.8 %) patients SRT, 31 (17.1 %) PT and 12 (6.7 %) EBRT. With a median follow-up of 4.6 years (interquartile range 1.7-6.8), 3-year s-PFS was 51.6 % and 3-year OS 72.5 %. At univariate analysis, SRT (HR 0.32, 95 % CI 0.19-0.55, p < 0.001), longer interval between the two courses of irradiation (HR 0.37, 95 % CI 0.21-0.67, p = 0.001), and higher tumor BED (HR 0.45 95 % CI 0.27-0.76, p = 0.003) were associated with longer s-PFS; in contrast, Ki67 > 5 % (HR 2.81, 95 % CI 1.48-5.34, p = 0.002) and WHO grade > 2 (HR 3.08, 95 % CI 1.80-5.28, p < 0.001) were negatively correlated with s-PFS. At multivariate analysis, SRT, time to re-RT and tumor BED maintained their statistically significant prognostic impact on s-PFS (HR 0.36, 95 % CI 0.21-0.64, p < 0.001; HR 0.38, 95 % CI 0.20-0.72, p = 0.003 and HR 0.31 95 % CI 0.13-0.76, p = 0.01, respectively). Acute and late adverse events (AEs) were reported in 38 (20.9 %) and 29 (16 %) patients. Larger tumor GTV (≥10 cc) was significantly associated with acute and late toxicity (p < 0.001 and p = 0.009, respectively).

CONCLUSIONS

In patients with recurrent meningiomas, reirradiation is a feasible treatment option associated with acceptable toxicity profile. Prognostic factors in the decision-making process have been identified and should be incorporated in daily practice.

Radiation-Induced Meningiomas

While the majority of meningiomas encountered clinically are sporadic, there is a rare subset that arises due to early life or childhood irradiation. Sources of this radiation exposure may be due to treatment of other cancers such as acute childhood leukemia, other central nervous system tumors such as medulloblastoma, the treatment of tinea capitis (rarely and historically), or environmental exposures, as seen in some of the Hiroshima and Nagasaki atomic bomb survivors. Regardless of their etiology, however, radiation-induced meningiomas (RIMs) tend to be highly biologically aggressive irrespective of WHO grade and are usually refractory to the conventional treatment modalities of surgery and/or radiotherapy. In this chapter, we will discuss these RIMs in their historical context, their clinical presentation, their genomic features and ongoing efforts to better understand these tumors from a biological standpoint in order to develop better, more efficacious therapies for these patients.

Stereotactic Therapies for Meningiomas

Although surgery remains the mainstay of treatment for most meningiomas, radiotherapy, specifically stereotactic radiosurgery, has become more commonplace as first-line therapy for select meningioma cases, particularly small meningiomas in challenging or high-risk anatomic locations. Radiosurgery for specific groups of meningiomas have been found to provide local control rates comparable to surgery alone. In this chapter stereotactic techniques for the treatment of meningiomas such as stereotactic radiosurgery by using Gamma knife or Linear Accelerator-based techniques (modified LINAC, Cyberknife, etc.) as well as stereotactically guided implantation or radioactive seeds for brachytherapy are introduced.

Stereotactic radiosurgery in the management of petroclival meningiomas: a systematic review and meta-analysis of treatment outcomes of primary and adjuvant radiosurgery

PURPOSE

To summarize the clinical features and outcomes of petroclival meningioma patients treated with stereotactic radiosurgery (SRS) as either a primary or an adjuvant modality.

METHODS

Relevant articles were retrieved from PubMed, Scopus, Web of Science, and Cochrane. A systematic review and meta-analysis of treatment outcomes comparing primary and adjuvant SRS was conducted.

RESULTS

Seven articles comprising 722 cases were included. The mean tumor marginal dose was 13.5 Gy. After SRS, symptoms improved in 28.7%, remained unchanged in 61.3%, and worsened in 10.0% of the cohort. Tumor control was achieved in 94.8% of patients. The mean tumor volume change was -6.4 cm³. The 5-year and 10-year progression-free survival (PFS) rates were 91-100% and 69.6-89.9%, respectively. Overall, 61.9% of patients underwent primary radiosurgery, and 38.1% had adjuvant radiosurgery. Patients who had primary SRS reported higher rates of tumor control (94.3% vs. 88.2%) and fewer SRS-related complications (3.7% vs. 10.3%) than those who received adjuvant SRS (not accounting for microsurgical complications). The functional status of patients who had primary SRS was more likely to improve or remain unchanged, with an effect size of 1.12 (95% CI 1.1-1.25; I² = 0). Neither group displayed superiority in worsening functional outcomes or tumor control rate.

CONCLUSION

SRS of petroclival meningiomas was associated with excellent long-term PFS and local tumor control rates. Primary SRS was highly effective for patients with smaller volume lesions without clinically symptomatic mass effect. In patients who warrant initial resection, adjuvant radiosurgery remains an important modality to prevent regrowth while maintaining postresection function.

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.

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.

Successful management of an intraluminal superior sagittal sinus meningioma causing elevated intracranial pressure using gamma knife radiosurgery in subacute setting: A case report

Background:

Gamma Knife stereotactic radiosurgery (GKRS) facilitates precisely focused radiation to an intracranial target while minimizing substantial off-target radiation in the surrounding normal tissue. Meningiomas attached to or invading the superior sagittal sinus may result in sinus occlusion and are often impossible to completely resect safely. The authors describe successful management of a patient with a meningioma located completely inside the posterior aspect of the superior sagittal sinus.

Case Description:

A 46-year-old woman presented to the emergency department with progressive generalized headaches accompanied by worsening vision. The patient underwent a diagnostic brain magnetic resonance imaging which showed a solitary a 7 × 6 × 10 mm homogeneously contrast-enhancing lesion within the lumen of the posterior aspect of superior sagittal sinus without ventricular enlargement or peritumoral edema. The lesion was thought to be a meningioma radiographically. To evaluate the suspected increased intracranial pressure, a lumbar puncture was subsequently performed and demonstrated an opening pressure of 30 cm H2O. After drainage of 40 cc of CSF, the spinal closing pressure was 9 cm H2O. After failure of conservative management with acetazolamide, and determination of surgical inoperability due to the critical intraluminal location of the mass lesion, the patient underwent Gamma Knife radiosurgery. The 0.36 cc tumor was treated as an outpatient in the Perfexion® model Gamma Knife with a highly conformal and selective plan that enclosed the 3D geometry of the tumor with a minimal margin tumor dose of 14 gy at the 50% isodose. Three months after GKRS, the patient reported continued reduction in the frequency and severity of both her headaches and her visual disturbance. Ophthalmological consultation noted progressive resolution of her optic disc edema confirmed by formal optical coherence tomography. The patient is now 3 years out from GKRS with complete resolution of headache symptoms along with persistent reduction in tumor size (3 × 1 × 4 mm) on serial period imaging and resolution of papilledema.

Conclusion:

Tumors located in such critical anatomic regions, as in our patient, should be considered for primary GKRS when the risks of biopsy or removal are too high. GKRS was able to provide great radiographic and clinical result in an intricately located meningioma.

Stereotactic Radiosurgery for Intracranial Noncavernous Sinus Benign Meningioma: International Stereotactic Radiosurgery Society Systematic Review, Meta-Analysis and Practice Guideline

BACKGROUND

Stereotactic radiosurgery (SRS) for benign intracranial meningiomas is an established treatment.

OBJECTIVE

To summarize the literature and provide evidence-based practice guidelines on behalf of the International Stereotactic Radiosurgery Society (ISRS).

METHODS

Articles in English specific to SRS for benign intracranial meningioma, published from January 1964 to April 2018, were systematically reviewed. Three electronic databases, PubMed, EMBASE, and the Cochrane Central Register, were searched.

RESULTS

Out of the 2844 studies identified, 305 had a full text evaluation and 27 studies met the criteria to be included in this analysis. All but one were retrospective studies. The 10-yr local control (LC) rate ranged from 71% to 100%. The 10-yr progression-free-survival rate ranged from 55% to 97%. The prescription dose ranged typically between 12 and 15 Gy, delivered in a single fraction. Toxicity rate was generally low.

CONCLUSION

The current literature supporting SRS for benign intracranial meningioma lacks level I and II evidence. However, when summarizing the large number of level III studies, it is clear that SRS can be recommended as an effective evidence-based treatment option (recommendation level II) for grade 1 meningioma.

Intraoperative MRI for the microsurgical resection of meningiomas close to eloquent areas or dural sinuses: patient series

BACKGROUND

Meningiomas are the most commonly encountered nonglial primary intracranial tumors. The authors report on the usefulness of intraoperative magnetic resonance imaging (iMRI) during microsurgical resection of meningiomas located close to eloquent areas or dural sinuses and on the feasibility of further radiation therapy.

OBSERVATIONS

Six patients benefited from this approach. The mean follow-up period after surgery was 3.3 (median 3.2, range 2.1–4.6) years. Five patients had no postoperative neurological deficit, of whom two with preoperative motor deficit completely recovered. One patient with preoperative left inferior limb deficit partially recovered. The mean interval between surgery and radiation therapy was 15.8 (median 16.9, range 1.4–40.5) months. Additional radiation therapy was required in five cases after surgery. The mean preoperative tumor volume was 38.7 (median 27.5, range 8.6–75.6) mL. The mean postoperative tumor volume was 1.2 (median 0.8, range 0–4.3) mL. At the last follow-up, all tumors were controlled.

LESSONS

The use of iMRI was particularly helpful to (1) decide on additional tumor resection according to iMRI findings during the surgical procedure; (2) evaluate the residual tumor volume at the end of the surgery; and (3) judge the need for further radiation and, in particular, the feasibility of single-fraction radiosurgery.

Long-term apparent diffusion coefficient value changes in patients undergoing radiosurgical treatment of meningiomas

PURPOSE

A noninvasive method to predict the progress or treatment response of meningiomas is desirable to improve the tumor management. Studies showed that apparent diffusion coefficient (ADC) pretreatment values can predict treatment response in brain tumors. The aim of this study was to analyze changes of intratumoral ADC values in patients with meningiomas undergoing conservative or radiosurgery.

METHOD

MR images of 51 patients with diagnose of meningiomas were retrospectively reviewed. Twenty-five patients undergoing conservative or radiosurgery treatment, respectively, were included in the study. The follow-up data ranged between 1 and 10 years. Based on ROI analysis, the mean ADC values, ADC_10%min, and ADC_90%max were evaluated at different time points during follow-up.

RESULTS

Baseline ADC values in between both groups were similar. The ADC_mean values, ADC_10%min, and ADC_90%max within the different groups did not show any significant changes during the follow-up times in the untreated (ADC_mean over 10 years period: 0.87 ± 0.05 × 10^-3 mm²/s) and radiosurgically treated (ADC_mean over 4 years period: 1.02 ± 0.12 × 10^-3 mm²/s) group. However, statistically significant difference was observed when comparing the ADC_mean and ADC_90%max values of untreated with radiosurgically treated (p < 0.0001) meningiomas. Also, ADC_10%min revealed statistically significant difference between the untreated and the radiosurgery group (p < 0.05).

CONCLUSIONS

ADC values in conservatively managed meningiomas remain stable during the follow-up. However, meningiomas undergoing radiosurgery reveal significant change of the mean ADC values over time, suggesting that ADC may reflect a change in the biological behavior of the tumor. These observations might suggest the value of ADC changes as an indicator of treatment response.

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.

Extent of Resection in Meningioma: Predictive Factors and Clinical Implications

Meningiomas present as intracranial extra-axial lesions with dural attachment, which are primarily managed surgically. The extent of resection (EOR) may vary depending on patient- and tumor-related factors. The aim of this study is to identify preoperative predictive factors of EOR and to propose an estimation of the predicted gross total resection (GTR) based of patient- and tumor-characteristics. 1469 patients from a retrospectively (1990 to 2002) and prospectively managed (2003 to 2010) databank of Oslo University Hospital, Norway, totalling 11,414 patient-years of follow-up were included. Patients had a mean age at surgery of 64 ± 20.1 years with a female-to-male ratio was 2.4:1 and a mean KPS of 81.2 ± 12.1. Skull-base meningiomas represented 47% of all cases. WHO grades were I in 92.3%, II in 5.2%, and III in 2.2%. Bone infiltration was described in 18.7% of cases. 39.3% of patients had Simpson I resection, 34.3% had Simpson II, 5.4% had Simpson III, 20.6% had Simpson IV, and 0.5% had Simpson V. The risk factors for incomplete resection were: symptomatic presentation (OR 0.56 [0.43-0.72]), skull-base location (OR 0.79 [0.70-0.88]), and bone invasion (OR 0.85 [0.73-0.99]). Using a recursive partitioning analysis, we propose a classification-tree for the prediction of GTR rate based on preoperatively determinable patient- and tumor characteristics. The identification of preoperative predictors of poor GTR rate may aid clinicians managing meningioma patients. In selected cases were the predicted GTR rate is low, staged treatment with surgical debulking followed by adjuvant therapy may be favored in order to minimize postoperative morbidity and mortality.

Value of K i -67 Labeling Index in Predicting Recurrence of WHO Grade I Cranial Base Meningiomas

Objectives  Assess impact of K _i -67 labeling index (LI; K _i -67 LI) on risk of recurrence or progression of WHO grade I meningiomas. Study Design  Retrospective study of adult patients who underwent resection of cranial base meningioma between 2004 and 2016. Results  272 patients fulfilled criteria for inclusion in the study. Average age was 61.8 years; 196 (72%) were females. Simpson's grade 1 resection was noted in 77 patients (32%), grade 2 in 39 (16%), grade 3 in 36 (15%), and grade 4 in 88 (37%). The K _i -67 LI was low (1-4%) in 214 (78.7%), intermediate (5-9%) in 44 (16.2%), and high (>10%) in 14 (5.2%). Median follow-up was 39 months (IQR: 16-71 months); 221 (87.1%) tumors remained stable or did not recur, 19 (7.4%) recurred, and 14 (5.5%) progressed. Compared with tumors with low K _i -67 LI, those with intermediate K _i -67 LI had 2.47 times (2.47 [1.09-5.59], p  = 0.03), and those with high K _i -67 LI had 3.38 times (3.38 [1.16-9.89], p  = 0.03) higher risk of recurrence or progression. Tumors with K _i -67 LI > 4% had a shorter time to recurrence or progression ( p  = 0.01). Recurrence or progression-free survival rates at 3, 5, and 10 years for tumors with low K _i -67 LI were 95%, 89%, and 75%, respectively; tumors with intermediate K _i -67 LI, 87%, 69%, and 52%, respectively; tumors with high K _i -67 LI, 78%, 49%, and 49%, respectively. Conclusions  Following surgical resection of a WHO grade I cranial base meningioma, K _i -67 LI > 4% may predict an increased risk of recurrence or progression of residual tumor.

Long-term stroke risk of single-fraction photon-based stereotactic radiosurgery for meningioma

OBJECTIVES

A recent randomized study of fractionated radiation therapy (RT) examining 44 subtotally resected/recurrent benign meningioma patients revealed that at median follow-up of 17.1 years, the risk of stroke following proton-photon RT was 20.5%; the average stroke developed 5.6 years following RT completion (Sanford et al., 2017). This stroke risk is up to 10 times higher than the 2-6% rate expected for the general population of ages 40-79 (Mozaffarian et al., 2015). The stroke rate following single-fraction stereotactic radiosurgery (SRS) has not been previously studied in meningioma patients.

PATIENTS AND METHODS

A PubMed database search for relevant articles examining SRS for meningioma with minimum mean/median follow-up of six years was undertaken. Stroke rate was assessed either from direct description in manuscripts, or from extrapolating post-SRS complications from reported clinical examinations (i.e. hemiparesis/weakness, pituitary dysfunction following treatment of cavernous sinus lesions). Results were then culled to determine an overall stroke rate.

RESULTS

Fourteen studies met inclusion criteria; 1431 patients received photon-based SRS for meningioma with a sufficient long-term follow-up. Median/mean follow-up ranged from 75 to 144 months. Operative resection prior to SRS occurred in 769/1377 patients (55.8%) for whom surgical history was reported. Twenty-four patients suffered a stroke following SRS, yielding a rate of 1.7%.

CONCLUSIONS

The long-term stroke rate following single-fraction photon-based SRS for benign meningioma was 1.7%, more than twelve times lower than for fractionated proton-photon RT and comparable to that expected for the general population. The majority of patients underwent resection prior to SRS. These findings indicate that for patients with benign meningioma desiring to avoid the high stroke risk of fractionated proton-photon RT, SRS has a comparable stroke risk profile to observation. Such findings are pertinent for radiation oncology, neuro-oncology, and neurosurgery management of these patients.

Three-dimensional multimodality fusion imaging as an educational and planning tool for deep-seated meningiomas

INTRODUCTION

The utility of surgical simulation with three-dimensional multimodality fusion imaging (3D-MFI) has been demonstrated. However, its potential in deep-seated brain lesions remains unknown. The aim of this study was to investigate the impact of 3D-MFI in deep-seated meningioma operations.

MATERIAL AND METHODS

Fourteen patients with deeply located meningiomas were included in this study. We constructed 3D-MFIs by fusing high-resolution magnetic resonance (MR) and computed tomography (CT) images with a rotational digital subtraction angiogram (DSA) in all patients. The surgical procedure was simulated by 3D-MFI prior to operation. To assess the impact on neurosurgical education, the objective values of surgical simulation by 3D-MFIs/virtual reality (VR) video were evaluated. To validate the quality of 3D-MFIs, intraoperative findings were compared. The identification rate (IR) and positive predictive value (PPV) for the tumor feeding arteries and involved perforating arteries and veins were also assessed for quality assessment of 3D-MFI.

RESULTS

After surgical simulation by 3D-MFIs, near-total resection was achieved in 13 of 14 (92.9%) patients without neurological complications. 3D-MFIs significantly contributed to the understanding of surgical anatomy and optimal surgical view (p < .0001) and learning how to preserve critical vessels (p < .0001) and resect tumors safety and extensively (p < .0001) by neurosurgical residents/fellows. The IR of 3D-MFI for tumor-feeding arteries and perforating arteries and veins was 100% and 92.9%, respectively. The PPV of 3D-MFI for tumor-feeding arteries and perforating arteries and veins was 98.8% and 76.5%, respectively.

CONCLUSIONS

3D-MFI contributed to learn skull base meningioma surgery. Also, 3D-MFI provided high quality to identify critical anatomical structures within or adjacent to deep-seated meningiomas. Thus, 3D-MFI is promising educational and surgical planning tool for meningiomas in deep-seated regions.

[Relevance of Simpson's grading system for resections in WHO grade I meningiomas]

OBJECT

The aim of this study is to assess if the recurrence rates and recurrence/progression-free survivals (RFS) are different after Simpson's grades I, II, III and IV resections in World Health Organization (WHO) grade I meningiomas.

MATERIAL AND METHODS

A retrospective review was conducted on the data of patients who underwent surgical treatment of WHO grade I meningiomas located in convexity, falx/parasagittal, and skull base (anterior/media/posterior) between June 1991 and December 2011. In Simpson's grade IV resections, surgical treatment was supplemented with radiotherapy/radiosurgery on the tumour remains. A comparison was made on the recurrence rates and RFSs between Simpson's grades I, II, III, and IV resections, both overall and in tumour subsets according to their location.

RESULTS

A total of 208 meningiomas were included in this study. There were no significant differences in recurrence rates and RFSs between Simpson's grades I, II, III, and IV. No significant differences were noted between the different degrees of Simpson in any of the location groups. In convexity meningiomas, the recurrence rates were 7% and 33% in Simpson's grades I and III resections, respectively (P=.131).

CONCLUSIONS

It has been shown that the rates of tumour control in meningiomas are not related to Simpson grades. In falx/parasagittal and skull base meningiomas, more aggressive attempts of tumour resection must be balanced against the risks of damaging critical neurovascular structures. In convexity meningiomas, a Simpson's grade I resection should be attempted first.

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.

Stereotactic radiosurgery for intracranial meningiomas: current concepts and future perspectives

Meningiomas are among the most common adult brain tumors. Although the optimal management of meningiomas would provide complete elimination of the lesion, this cannot always be accomplished safely through resection. Therefore, other therapeutic modalities, such as stereotactic radiosurgery (as primary or adjunctive therapy), have emerged. In the current review, we have provided an overview of the historical outcomes of various radiosurgical modalities applied in the management of meningiomas. Furthermore, we provide a discussion on key factors (eg World Health Organization grade, lesion size, and lesion location) that affect tumor control and adverse event rates. We discuss recent changes in our understanding of meningiomas, based on molecular and genetic markers, and how these will change our perspective on the management of meningiomas. We conclude by outlining the areas in which knowledge gaps persist and provide suggestions as to how these can be addressed.

Partial skull base tumour resection in combination with radiosurgery: an escape procedure or a reasonable solution of treatment?

Despite advancement in microsurgical techniques for skull base tumour surgery, approaches of this kind still represent a significant challenge for neurosurgeons due to the size of the tumour and its interference and proximity to important neural and vascular structures. After incomplete resection, gamma knife radiosurgery is becoming an alternative or adjunctive treatment option. In this article, some examples of our experience in combined treatment of the skull base tumours with surgical procedure and gamma knife therapy for the remaining tumour tissue are presented.

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.

Meningiomas: knowledge base, treatment outcomes, and uncertainties. A RANO review

Evolving interest in meningioma, the most common primary brain tumor, has refined contemporary management of these tumors. Problematic, however, is the paucity of prospective clinical trials that provide an evidence-based algorithm for managing meningioma. This review summarizes the published literature regarding the treatment of newly diagnosed and recurrent meningioma, with an emphasis on outcomes stratified by WHO tumor grade. Specifically, this review focuses on patient outcomes following treatment (either adjuvant or at recurrence) with surgery or radiation therapy inclusive of radiosurgery and fractionated radiation therapy. Phase II trials for patients with meningioma have recently completed accrual within the Radiation Therapy Oncology Group and the European Organisation for Research and Treatment of Cancer consortia, and Phase III studies are being developed. However, at present, there are no completed prospective, randomized trials assessing the role of either surgery or radiation therapy. Successful completion of future studies will require a multidisciplinary effort, dissemination of the current knowledge base, improved implementation of WHO grading criteria, standardization of response criteria and other outcome end points, and concerted efforts to address weaknesses in present treatment paradigms, particularly for patients with progressive or recurrent low-grade meningioma or with high-grade meningioma. In parallel efforts, Response Assessment in Neuro-Oncology (RANO) subcommittees are developing a paper on systemic therapies for meningioma and a separate article proposing standardized end point and response criteria for meningioma.

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.

The evolving role of radiosurgery in the management of radiation-induced meningiomas: a review of current advances and future directions

Meningiomas are among the most common primary adult brain tumors, which arise either spontaneously or secondary to environmental factors such as ionizing radiation. The latter are referred to as radiation-induced meningiomas (RIMs) which, while much less common than their spontaneous counterparts, are challenging from a management point of view. Similar to spontaneous meningiomas, the optimal management of RIMs is complete surgical resection. However, given their high grade, multiplicity, tendency to invade bone and venous sinuses, and high recurrence rate, this cannot always be accomplished safely. Therefore, other therapeutic modalities, such as stereotactic radiosurgery, have emerged. In the current review, we provide an overview of the historical outcomes achieved for RIMs through radiosurgery and microsurgical resection. Furthermore, we provide a discussion of clinical and radiological parameters that affect the decision-making process with regard to the management of RIMs. We also provide an outline of recent changes in our understanding of RIMs, based on molecular and genetic markers, and how these will change our management perspective. We conclude the review by summarizing some of the current obstacles in the management of RIMs with SRS and how current and future research can address these challenges.

Petroclival meningiomas: an update on surgical approaches, decision making, and treatment results

OBJECT

Petroclival meningiomas remain a formidable challenge for neurosurgeons because of their location deep within the skull base and proximity to eloquent neurovascular structures. Various skull base approaches have been used in their treatment, and deciding which is the optimal one remains controversial. Attempts at achieving gross- or near-total resections are associated with an increased rate of morbidity and mortality. As adjunctive treatment options such as stereotactic radiosurgery have been developed and become widely available, there has been a trend toward accepting subtotal resections in an effort to minimize neurological morbidity. This paper reviews a recent series of patients with petroclival meningiomas and highlights current management trends and important considerations useful in surgical decision making.

METHODS

The records of patients with large (> 3 cm) petroclival meningiomas surgically treated by the senior author over the past 5 years were reviewed. The clinical results are presented as examples of the surgical approaches available for approaching these tumors, and treatment options are reviewed.

RESULTS

Of 196 meningiomas surgically treated during the study period, 8 lesions in 8 patients met the study criteria. Overall clinical results were excellent, with no death or major morbidity. Intracranial gross- or near-total resection (Simpson Grade 1, 2, or 3) was achieved in 5 patients (67%). New cranial nerve deficits occurred in 3 patients (37%) and were more common in patients in whom a subtotal resection was performed (2 of 3 cases). A variety of surgical approaches were used. Important considerations determining the best approach include the location of the tumor relative to the internal auditory canal, the presence of preoperative hearing loss, and the location of the tumor relative to the tentorium.

CONCLUSIONS

Achieving gross- or near-total resections of large petroclival meningiomas remains achievable and should be the primary goal of surgical treatment. A retrosigmoid craniotomy remains a workhorse surgical approach for most petroclival tumors of any size. Tumors that are medial to the internal auditory canal and span both middle and posterior cranial fossae are often best treated with a combined transpetrosal approach, which is especially true if there is a preoperative hearing deficit.

A review of stereotactic radiosurgery practice in the management of skull base meningiomas

Gross total resection of skull base meningiomas poses a surgical challenge due to their proximity to neurovascular structures. Once the gold standard therapy for skull base meningiomas, microsurgery has been gradually replaced by or used in combination with stereotactic radiosurgery (SRS). This review surveys the safety and efficacy of SRS in the treatment of cranial base meningiomas including 36 articles from 1991 to 2010. SRS produces excellent tumor control with low morbidity rates compared with surgery alone for asymptomatic small skull base meningiomas, patients with risk factors precluding conventional surgery, and as adjuvant therapy for recurrent or residual lesions.

Multi-session radiosurgery of benign intracranial tumors

Multi-session stereotactic radiosurgery (SRS) enables a high dose per fraction to be delivered to the tumor bed with rapid dose falloff that allows for sparing of critical structures, resulting in less radiation-associated toxicity. In this article, the authors review the basic concepts and techniques of multi-session SRS, indications for this technique, outcomes from single-session and multi-session SRS using 3 commonly treated benign intracranial tumors (meningiomas, vestibular schwannomas, pituitary adenomas), and discuss why multi-session SRS is an attractive approach for the treatment of these tumors.

Reirradiation of recurrent meningioma

Management of meningioma includes observation, resection, and radiation therapy (RT). For patients with recurrent disease, similar options exist. However, the control rate following a second course of RT for recurrent disease is unknown. We reviewed an institutional database of patients with meningioma treated with stereotactic radiosurgery or fractionated stereotactic RT who underwent a second course for recurrent disease. Cox regression model was used for analysis. Variables tested included tumor volume, RT type, tumor grade, age at diagnosis, time to progression, and interval between RT. Eleven of 19 patients (58%) experienced disease progression. Median time to second progression was 10 months. Freedom from progression at one year was lower in patients with grade II or III tumors compared to those with grade 1 or unknown histology (17% compared to 92%, p=0.0054). Cox regression showed that a grade II-III tumor affects progression-free survival (PFS), with a hazard ratio of 5.37 (p=0.011). Median time to progression (MTP) for patients with grade II-III tumors was eight months. MTP was not reached for patients with grade 1/unknown tumors. Reirradiation for recurrent meningioma yields modest tumor control rates but for patients with grade II or III tumors, outcomes are poor.

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.

Molecular genetics of meningiomas: a systematic review of the current literature and potential basis for future treatment paradigms

Although a majority of meningiomas are benign neoplasms, those occurring at the cranial base may be challenging tumors to treat because of extensive tissue invasion, an inability to achieve gross-total microscopic resection, and local tumor recurrence and/or progression. A more comprehensive understanding of the genetic abnormalities associated with meningioma tumorigenesis, growth, and invasion may provide novel targets for grading assessments and individualizing molecular therapies for skull base meningiomas. The authors performed a review of the current literature to identify genes that have been associated with the formation and/or progression of meningiomas. Mutations in the NF2 gene have been most commonly implicated in the formation of the majority of meningiomas. Inactivation of other tumor suppressor genes, including DAL-1 and various tissue inhibitors of matrix metalloproteinases, upregulation of several oncogenes including c-sis and STAT3, and signaling dysregulation of pathways such as the Wnt pathway, have each been found to play important, and perhaps, complementary roles in meningioma development, progression, and recurrence. Identification of these genetic factors using genome-wide association studies and high-throughput genomics may provide data for future individualized treatment strategies.

Long-term outcomes and patterns of tumor progression after gamma knife radiosurgery for benign meningiomas

OBJECT

To characterize the timing and patterns of long-term treatment failure after Gamma Knife radiosurgery (GKRS) for benign meningiomas.

METHODS

Data were retrospectively reviewed in 116 patients who underwent 136 GKRS treatments for benign intracranial meningiomas from 1996 to 2004. Patients with atypical or malignant meningiomas were excluded. Surgical resection preceded GKRS in 72 patients (62%). The median tumor volume was 3.4 cm, and the median prescription dose to the 50% isodose line was 16 Gy.

RESULTS

The median follow-up time was 75 months (range, 4-146 months). Overall tumor control was achieved in 128 of 136 lesions (94%), of which tumor size was stable in 68% and decreased in 26%. Seven patients experienced disease progression in 8 tumors, occurring at a mean time of 90 months. The overall 5-year and 10-year actuarial tumor control rate was 98.9% and 84%, respectively. Characteristics corresponding to tumor progression included insufficient tumor coverage (98% vs 93%, P = .007), cavernous sinus lesions, and meningiomatosis. Complications after GKRS developed in 8% of patients, in whom the mean tumor volume was nearly double that in patients with no adverse effects (11 vs 5.7 cm3, P = .003).

CONCLUSIONS

GKRS demonstrates excellent long-term tumor control in the management of benign meningiomas. Tumor progression occurred at a mean time of 7.5 years after GKRS, reinforcing the need for long-term surveillance despite initial tumor control. Treatment failure was related to undercoverage of lesions in the majority of cases, with the remainder demonstrating evidence of abnormal tumor biology.

Combined Endoscopic Endonasal Surgery and Fractionated Stereotactic Radiosurgery (fSRS) for Complex Cranial Base Tumors—Early Clinical Outcomes

Endoscopic endonasal surgery (EES) has been shown to be a feasible approach to cranial base tumors while reducing post-operative morbidity. Using the endoscopic endonasal approach alone or in combination with open approaches may provide advantages over conventional approaches. However, the balance between maximal resection and minimal injury to neurovascular structures frequently precludes gross total resection (GTR). Consequently, adjuvant radiation therapy may be an important option to improve local control (LC) of residual disease. In this retrospective series, we report clinical outcomes, morbidity, and LC of 40 patients with cranial base tumors treated with EES +/- combined open approach followed by fSRS (CyberKnife, Accuray Inc.). 26 patients had benign disease, 7 had newly diagnosed malignant disease, and 7 had previously resected malignant disease. Surgical outcomes were evaluable in all patients. LC after fSRS was evaluable in 39 patients and defined as no evidence of regrowth by MRI, CT, & physical examination. GTR was achieved in 12/40. Median post-operative length of stay (LOS) was 3 days. In multivariable analysis controlling for anatomic location and malignant histology, post-operative complications (n = 10) were significantly associated with patients having combined open and EES (p < 0.01, OR = 16.9). SRS was delivered in 1–5 sessions to a median marginal dose of 24.9 Gy. Median follow-up was 24.7 months (range, 1.5 to 61 months). LC was achieved in 89.7% (35/39) of evaluable patients. LC was achieved in 11/12 patients who had GTR. Median progression-free survival was 19.7 months (21.0 months for benign tumors (n = 26), 5.8 months for previously resected malignant disease (n = 7), and 21.2 months for newly diagnosed malignant disease (n = 7). Of the 31 patients who had symptomatic disease at presentation, 18 (58%) reported complete symptom resolution, 9 partial, and 4 no improvement. One patient who received two prior courses of radiation therapy developed osteosclerosis (grade III). Other adverse events were erythema (grade I, n = 5), nausea (grade II, n = 2), conjunctivitis (grade II, n = 1). EES followed by fSRS is a safe and effective management strategy for selected cranial base tumors. EES combined with an open surgical approach may result in increased complications. However, initial follow-up offers encouraging results indicating shorter time to recovery, acceptable LC rates compared to conventional approaches, and similar median time to progression for benign and newly diagnosed malignant disease.

Stereotactic radiosurgery for skull base meningioma

Stereotactic radiosurgery is now a treatment option for meningiomas, especially for high-risk patients such as those with skull base lesions. The clinical outcomes were retrospectively analyzed of stereotactic radiosurgery using the Leksell Gamma Knife((R)) performed for 98 patients with 106 skull base meningiomas at the University of Tokyo Hospital between June 1990 and April 2006 and followed up for more than a year. After a median follow-up period of 53.2 months (range 12.2-204.4 months), local tumor control rates were 86.9% and 78.9% at 5 years and 10 years, respectively. Tumors with volume of 4 cm(3) or smaller (97.5% vs. 76.1% at 5 years, p = 0.001) and tumors completely included within the isodose line of 14 Gy or more (97.5% vs. 67.2% at 5 years, p = 0.0006) had higher local control rates. Postoperative residual tumors treated by stereotactic radiosurgery were controlled in all 25 cases. Cranial nerve deficits were improved, stable, and deteriorated in 12, 64, and 3 patients, respectively, after stereotactic radiosurgery. Stereotactic radiosurgery was effective treatment method for local control of skull base meningiomas, especially for small or postoperative residual tumors. Correct combination of microsurgery and radiosurgery leads to excellent local control.

MULTISESSION CYBERKNIFE STEREOTACTIC RADIOSURGERY OF LARGE, BENIGN CRANIAL BASE TUMORS

OBJECTIVE

Although radiosurgery plays an important role in managing benign cranial base lesions, the potential for increased toxicity with single-session treatment of large tumors is a concern. In this retrospective study, we report the intermediate-term rate of local control, morbidity, and clinical outcomes of patients with large cranial base tumors treated with multisession stereotactic radiosurgery with the CyberKnife (Accuray, Inc., Sunnyvale, CA).

METHODS

Between 1999 and 2008, 34 consecutive patients with large (&gt;15 cm3), benign cranial base tumors (21 meningiomas, 9 schwannomas, 4 glomus jugulare tumors) underwent primary or postoperative radiosurgical treatment using a multisession approach at Stanford University and were considered in this retrospective study. Forty-four percent of these patients had undergone previous subtotal surgical resection or radiotherapy. CyberKnife radiosurgery was delivered in 2 to 5 sessions (median, 3 sessions) to a median tumor volume of 19.3 cm3 (range, 15.8–69.3 cm3). The median marginal dose was 24 Gy (range, 18–25 Gy) prescribed to a median 78% isodose line.

RESULTS

After a median clinical follow-up of 31 months (range, 12–77 months), 21% of patients experienced clinical improvement of neurological symptoms, whereas neurological status remained unchanged among the rest. Four patients experienced prolonged use of glucocorticoids owing to transient neurological worsening and radiographic signs of radiation injury. No permanent neurotoxicity was seen. To date, all tumors remain locally controlled.

CONCLUSION

Over our modest length of follow-up, multisession radiosurgery appears to be a safe and effective option for selected large, benign brain and cranial base lesions.

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.