Stereotactic radiosurgery of meningiomas following resection: predictors of progression

Proton therapy for intracranial meningioma: a single-institution retrospective analysis of efficacy, survival and toxicity outcomes

PURPOSE

To report the outcomes of a large series of intracranial meningiomas (IMs) submitted to proton therapy (PT) with curative intent.

METHODS

We conducted a retrospective analysis on all consecutive IM patients treated between 2014 and 2021. The median PT prescription dose was 55.8 Gy relative biological effectiveness (RBE) and 66 GyRBE for benign/radiologically diagnosed and atypical/anaplastic IMs, respectively. Local recurrence-free survival (LRFS), distant recurrence-free survival (DRFS), overall survival (OS), and radionecrosis-free survival (RNFS) were evaluated with the Kaplan-Meier method. Univariable analysis was performed to identify potential prognostic factors for clinical outcomes. Toxicity was reported according to the latest Common Terminology Criteria for Adverse Events (CTCAE) version 5.0.

RESULTS

Overall, 167 patients were included. With a median follow-up of 41 months (range, 6-99), twelve patients (7%) developed tumor local recurrence after a median time of 39 months. The 5-year LRFS was 88% for the entire cohort, with a significant difference between benign/radiologically diagnosed and atypical/anaplastic IMs (98% vs. 47%, p < 0.001); this significant difference was maintained also for the 5-year OS and the 5-year DRFS rates. Patients aged ≤ 56 years reported significantly better outcomes, whereas lower prescription doses and skull base location were associated with better RNFS rates. Two patients experienced G3 acute toxicities (1.2%), and three patients G3 late toxicities (1.8%). There were no G4-G5 adverse events.

CONCLUSION

PT proved to be effective with an acceptable toxicity profile. To the best of our knowledge this is one of the largest series including IM patients submitted to PT.

Robotic Stereotactic Radiotherapy for Intracranial Meningiomas-An Opportunity for Radiation Dose De-Escalation

OBJECTIVE

To evaluate the possibility of dose de-escalation, with consideration of the efficacy and safety of robotic stereotactic CyberKnife radiotherapy in patients diagnosed with intracranial meningiomas.

METHODS

The study group consisted of 172 patients (42 men and 130 women) treated in III Radiotherapy and Chemotherapy Clinic of Maria Sklodowska-Curie National Research Institute of Oncology in Gliwice between January 2011 and July 2018. The qualification for dose de-escalation was based on MRI (magnetic resonance imaging) features: largest tumor diameter less than 5 cm, well-defined tumor margins, no edema, and no brain infiltration. The age of patients was 21-79 years (median 59 years) at diagnosis and 24-80 years (median 62 years) at radiotherapy. Sixty-seven patients (Group A) were irradiated after initial surgery. Histopathological findings were meningioma grade WHO 1 in 51 and WHO 2 in 16 cases. Group B (105 patients) had no prior surgery and the diagnosis was based on the typical features of meningioma on MRI. All patients qualified for the robotic stereotactic CyberKnife radiotherapy, and the total dose received was 18 Gy in three fractions to reference isodose 78-92%.

RESULTS

Follow-up period was 18 to 124 months (median 67.5 months). Five- and eight-year progression free survival was 90.3% and 89.4%, respectively. Two patients died during the follow-up period. Progression of tumor after radiotherapy was registered in 16 cases. Four patients required surgery due to progressive disease, and three of them were progression free during further follow-up. Twelve patients received a second course of robotic radiotherapy, 11 of them had stable disease, and one patient showed further tumor growth but died of heart failure. Crude progression free survival after both primary and secondary treatment was 98.8%. Radiotherapy was well-tolerated: acute toxicity grade 1/2 (EORTC-RTOG scale) was seen in 10.5% of patients. We did not observe any late effects of radiotherapy.

CONCLUSION

Stereotactic CyberKnife radiotherapy with total dose of 18 Gy delivered in three fractions showed comparable efficacy to treatment schedules with higher doses. This could support the idea of dose de-escalation in the treatment of intracranial meningiomas.

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

Background

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

Conclusion

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

Meningiomas

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

Prognostic value of the Simpson grading scale in modern meningioma surgery: Barrow Neurological Institute experience

OBJECTIVE

Recently, the prognostic value of the Simpson resection grading scale has been called into question for modern meningioma surgery. In this study, the authors analyzed the relationship between Simpson resection grade and meningioma recurrence in their institutional experience.

METHODS

This study is a retrospective review of all patients who underwent resection of a WHO grade I intracranial meningioma at the authors' institution from 2007 to 2017. Binary logistic regression analysis was used to assess for predictors of Simpson grade IV resection and postoperative neurological morbidity. Cox multivariate analysis was used to assess for predictors of tumor recurrence. Kaplan-Meier analysis and log-rank tests were used to assess and compare recurrence-free survival (RFS) of Simpson resection grades, respectively.

RESULTS

A total of 492 patients with evaluable data were included for analysis, including 394 women (80.1%) and 98 men (19.9%) with a mean (SD) age of 58.7 (12.8) years. The tumors were most commonly located at the skull base (n = 302; 61.4%) or the convexity/parasagittal region (n = 139; 28.3%). The median (IQR) tumor volume was 6.8 (14.3) cm3. Simpson grade I, II, III, or IV resection was achieved in 105 (21.3%), 155 (31.5%), 52 (10.6%), and 180 (36.6%) patients, respectively. Sixty-three of 180 patients (35.0%) with Simpson grade IV resection were treated with adjuvant radiosurgery. In the multivariate analysis, increasing largest tumor dimension (p < 0.01) and sinus invasion (p < 0.01) predicted Simpson grade IV resection, whereas skull base location predicted neurological morbidity (p = 0.02). Tumor recurrence occurred in 63 patients (12.8%) at a median (IQR) of 36 (40.3) months from surgery. Simpson grade I resection resulted in superior RFS compared with Simpson grade II resection (p = 0.02), Simpson grade III resection (p = 0.01), and Simpson grade IV resection with adjuvant radiosurgery (p = 0.01) or without adjuvant radiosurgery (p < 0.01). In the multivariate analysis, Simpson grade I resection was independently associated with no tumor recurrence (p = 0.04). Simpson grade II and III resections resulted in superior RFS compared with Simpson grade IV resection without adjuvant radiosurgery (p < 0.01) but similar RFS compared with Simpson grade IV resection with adjuvant radiosurgery (p = 0.82). Simpson grade IV resection with adjuvant radiosurgery resulted in superior RFS compared with Simpson grade IV resection without adjuvant radiosurgery (p < 0.01).

CONCLUSIONS

The Simpson resection grading scale continues to hold substantial prognostic value in the modern neurosurgical era. When feasible, Simpson grade I resection should remain the goal of intracranial meningioma surgery. Simpson grade IV resection with adjuvant radiosurgery resulted in similar RFS compared with Simpson grade II and III resections.

Does the Timing of Radiosurgery after Grade 1 Meningioma Resection Affect Long-Term Outcomes?

BACKGROUND

Meningiomas are the most common benign intracranial tumors. Gamma Knife® stereotactic radiosurgery (GKSRS) has become a preferred management for recurrent or residual meningiomas. This study focuses on the relationship between tumor control and the time interval between resection of a World Health Organization (WHO) grade 1 meningioma and GKSRS.

METHODS

This single institution retrospective analysis reviewed our experience in 238 patients who underwent GKSRS after a pathologically confirmed WHO grade 1 meningioma resection. The median follow-up was 7.4 years. The median aggregate tumor volume at GKSRS was 6 cm3 and a median margin dose of 13 Gy was utilized. Neurological symptoms were evident in 60% of patients at the time of procedure.

RESULTS

Overall actuarial tumor control rates achieved were 91.3% at 5 years, 83.4% at 10 years, and 76% at 15 years. There were 35 patients (15%) who developed tumor progression within or directly adjacent to the GKSRS treatment field. The median time until progression was 6.3 years. The duration between surgical intervention and GKSRS did not show statistical significance at 3 months (p = 0.9), 6 months (p = 0.8), 12 months (p = 0.5), or 24 months (p = 0.9). Fifteen patients (6%) had tumor progression at an anatomically distinct location outside the GKSRS target volume. Neurological symptomatic improvement was more likely with early radiosurgery intervention (p = 0.007).

CONCLUSION

Postoperative GKSRS was associated with excellent long-term tumor control for WHO grade 1 meningiomas, regardless of the interval after initial surgery. In addition, earlier radiosurgery was associated with superior symptom improvement.

Pathologic Characteristics Associated With Local Recurrence of Atypical Meningiomas Following Surgical Resection

Background

Optimal management of grade II meningiomas following resection remains controversial, owing mostly to the heterogeneity of post-operative (post-op) recurrence patterns across studies. Improved risk stratification of these patients would ensure that only those most at risk of recurrence would undergo appropriate post-op radiation therapy (RT).

Methods

Medical records from patients who underwent resection for grade II meningiomas were retrospectively reviewed. Demographic, disease characteristics, treatment, and clinical course data were retrospectively collected. Logistic regression, Cox proportional hazards modeling, and Kaplan-Meier curves with log rank testing were conducted to describe any potential relationships with time of recurrence.

Results

Of the 49 patients identified, 18 (36.7%) suffered a local recurrence following resection with a median follow-up of 3.1 years (range: 0.23 - 17.1 years). Past recurrence of the meningioma (P = 0.002) and extent of resection (P = 0.02) were significantly associated with local recurrence. On multivariable analysis, only prior meningioma recurrence was associated with time to local failure (P = 0.021). No histopathologic factors were found to be associated with the initial local failure. Of those who suffered a local recurrence, the presence of bone invasion (hazard ratio: 0.069, P = 0.008) and lack of salvage RT (P = 0.02) were associated with subsequent local failure.

Conclusions

Currently considered histopathologic factors appear not to be helpful in guiding initial treatment course. History of prior local failure and bone invasion appear to be associated with multiple recurrences. Optimal surgical resection is critical to improving outcomes, and salvage RT may reduce subsequent local failure.

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.

Proton Therapy for Intracranial Meningioma for the Treatment of Primary/Recurrent Disease Including Re-Irradiation

Meningeal tumors represent approximately 10-25% of primary brain tumors and occur usually in elderly female patients. Most meningiomas are benign (80-85%) and for symptomatic and/or large tumors, surgery, with or without radiation therapy (RT), has been long established as an effective means of local tumor control. RT can be delivered to inoperable lesions or to those with non-benign histology and for Simpson I-III and IV-V resection. RT can be delivered with photons or particles (protons or carbon ions) in stereotactic or non-stereotactic conditions. Particle therapy delivered for these tumors uses the physical properties of charged carbon ions or protons to spare normal brain tissue (i.e. Bragg peak), with or without or a dose-escalation paradigm for non-benign lesions. PT can substantially decrease the dose delivered to the non-target brain tissues, including but not limited to the hippocampi, optic apparatus or cochlea. Only a limited number of meningioma patients have been treated with PT in the adjuvant or recurrent setting, as well as for inoperable lesions with pencil beam scanning and with protons only. Approximately 500 patients with image-defined or WHO grade I meningioma have been treated with protons. The reported outcome, usually 5-year local tumor control, ranges from 85 to 99% (median, 96%). For WHO grade II or III patients, the outcome of only 97 patients has been published, reporting a median tumor local control rate of 52% (range, 38-71.1). Only 24 recurring patients treated previously with photon radiotherapy and re-treated with PT were reported. The clinical outcome of these challenging patients seems interesting, provided that they presented initially with benign tumors, are not in the elderly category and have been treated previously with conventional radiation dose of photons. Overall, the number of meningioma patients treated or-re-irradiated with this treatment modality is small and the clinical evidence level is somewhat low (i.e. 3b-5). In this review, we detail the results of upfront PT delivered to patients with meningioma in the adjuvant setting and for inoperable tumors. The outcome of meningioma patients treated with this radiation modality for recurrent tumors, with or without previous RT, will also be reviewed.

Evaluation of radiological recurrence patterns following gamma knife radiosurgery for solitary meningioma previously treated via cranial surgery

The use of gamma knife radiosurgery (GKS) for meningiomas after cranial surgery has been extensively evaluated; however, studies on tumor progression, including recurrence out of the margin dose line, are scarce. Hence, we aimed to evaluate the meningioma recurrence after GKS within and out of the margin dose. We included 37 consecutive patients with World Health Organization (WHO) grade 1 meningiomas who were treated with GKS following cranial surgery. Radiologically indicated recurrences were classified into three patterns by their relationship to the margin dose and tumor. The median follow-up was 58.9 months; 2 (5.4%) patients died. Only 2 (5.4%) patients did not keep active daily lives because of tumor progression. Cumulative local control at 5 years was 85.2%. Local recurrence and recurrence out of the margin dose occurred in 5 (13.5%) and 13 (35.1%) patients, respectively. A larger preoperative maximum diameter was a risk factor for local recurrence (hazard ratio [HR]: 2.118; P = 0.033), adjacent progression (HR: 1.633; P = 0.015), and remote progression (HR: 2.016; P = 0.003). Symptomatic adverse radiation effects occurred in 1 patient. Salvage GKS and cranial surgery were performed in 9 (24.3%) and 8 (21.6%) patients, respectively. Progression to WHO grade 2-3 occurred in 5 (13.5%) patients. A larger preoperative maximum diameter was a risk factor for progression of WHO grade (HR: 2.016, P = 0.033). Progression out of the margin dose was associated with a larger preoperative tumor size.

Factors Associated with Treatment Failure and Radiosurgery-Related Edema in WHO Grade 1 and 2 Meningioma Patients Receiving Gamma Knife Radiosurgery

BACKGROUND

Before the advent of radiosurgery, neurosurgical treatment of meningiomas typically involved gross total resection of the mass whenever surgery was deemed possible. Over the past 4 decades, though, Gamma Knife radiosurgery (GKRS) has proved to be an effective, minimally invasive means to control the growth of these tumors. However, the variables associated with treatment failure (regrowth or clinical progression) after GKRS and GKRS-related complications, such as cerebral edema, are less well understood.

METHODS

We retrospectively collected data between 2009 and 2018 for patients who underwent GKRS for meningiomas. After data collection, we performed univariate and multivariable modeling of the factors that predict treatment failure and cerebral edema after GKRS. Hazard ratios (HR) and P values were determined for these variables.

RESULTS

Fifty-two patients were included our analysis. The majority of patients were female (38/52,73%), and nearly all patients presented with a suspected or confirmed World Health Organization grade 1 meningioma (48/52, 92%). The median tumor volume was 3.49 cc (range, 0.22-20.11 cc). Evidence of meningioma progression after treatment developed in 5 patients (10%), with a median time to continued tumor growth of 5.9 months (range, 2.7-18.3 months). In multivariable analysis, patients in whom treatment failed were more likely to be male (HR = 8.42, P = 0.045) and to present with larger tumor volumes (HR = 1.27, P = 0.011). In addition, 5 patients (10%) experienced treatment-related cerebral edema. On univariate analysis, patients who experienced cerebral edema were more likely present with larger tumors (HR = 1.16, P = 0.028).

CONCLUSIONS

Increasing meningioma size and male gender predispose to meningioma progression after treatment with GKRS. Increasing tumor size also predicts the development of postradiosurgery cerebral edema.

Cranial Nerve Outcomes After Surgery for Frontal Skull Base Meningiomas: The Eternal Quest of the Maximum-Safe Resection with the Lowest Morbidity

OBJECTIVE

Maximal aggressive meningioma resection has been suggested to provide the best tumor control rates. However, radical surgery of meningiomas located at the frontal skull base can be accompanied by impairment of adjacent cranial nerve function that negatively affects patients' quality of life. We, therefore, analyzed our institutional database for cases of new cranial nerve deficits and postoperative cerebrospinal fluid (CSF) leakage stratified by the extent of tumor resection.

METHODS

From February 2009 to April 2017, 195 patients underwent resection of frontal skull base meningioma at our institution. Postoperative new deficits of cranial nerve function and CSF leakage were stratified by the resection into Simpson grade I resection with excision of the dural tail as an aggressive surgical approach and Simpson grade II-V resection.

RESULTS

Simpson grade I resection was associated with a significantly greater percentage of new cranial nerve deficits immediately after surgery (30%) compared with Simpson grade II (13%; P = 0.007) and Simpson grade II-V (17%; P = 0.035). The differences were greater at the 12-month follow-up point (29% Simpson grade I, 6% Simpson grade II [P < 0.001]; 10% Simpson grade II-V [P = 0.001]). Postoperative CSF leakage occurred in 10.1% of Simpson grade I versus 2.3% of Simpson grade II resections (P = 0.048). The retreatment rates did not differ between these 2 groups (2.5% vs. 3.4%; P = 1.000).

CONCLUSIONS

We found high levels of new cranial nerve morbidity and CSF leakage after radical removal of frontal skull base meningiomas that included the adjacent dura. Thus, less aggressive surgery for frontobasal meningioma should be preferred.

The evolution of cranial meningioma surgery-a single-center 25-year experience

BACKGROUND

There have been major developments in diagnostic and surgical and non-surgical techniques used in the management of meningiomas over last three decades. We set out to describe these changes in a systematic manner.

METHOD

Clinical and radiological data, surgical procedures, complications, and outcome of 817 patients who underwent surgery for primarily diagnosed meningioma between 1991 and 2015 were investigated.

RESULTS

Median age at diagnosis increased significantly from 56 to 59 years (p = .042), while tumor location and preoperative Karnofsky performance status did not change during the observation period. Availability of preoperative MRI increased, and rates of angiography and tumor embolization decreased (p < .001, each). Median duration of total, pre-, and postoperative stay was 13, 2, and 9 days, respectively, and decreased between 1991 and 2015 (p < .001, each). Median incision-suture time varied annually (p < .001) but without becoming clearly longer or shorter during the entire observation period. The use of intraoperative neuronavigation and neuromonitoring increased, while the rates of Simpson grade I and III surgeries decreased (p < .001). Rates of postoperative hemorrhage (p = .997), hydrocephalus (p = .632), and wound infection (p = .126) did not change, while the frequency of early postoperative neurological deficits decreased from 21% between 1991 and 1995 to 13% between 2011 and 2015 (p = .003). During the same time, the rate of surgeries for postoperative cerebrospinal fluid leakage slightly increased from 2 to 3% (p = .049). Within a median follow-up of 62 months, progression was observed in 114 individuals (14%). Progression-free interval did not significantly change during observation period (p > .05). Multivariate analyses confirmed the lack of correlation between year of surgery and tumor relapse (HR: 1.1, p > .05).

CONCLUSIONS

Preoperative diagnosis and surgery of meningiomas have been substantially evolved. Although early neurological outcome has improved, long-term prognosis remains unchanged.

Gamma Knife Stereotactic Radiosurgery for Grade 2 Meningiomas

Purpose  This study aims to report long-term clinical outcomes after Gamma Knife radiosurgery (GKRS) for intracranial grade 2 meningiomas. Methods  In this Institutional Review Board approved study, we reviewed records of all patients with grade 2 meningiomas treated with GKRS between 1998 and 2014. Results  A total of 97 postoperative histopathologically confirmed grade 2 meningiomas in 75 patients were treated and are included in this study. After a mean follow-up of 41 months, 28 meningiomas had local recurrence (29.79%). Median time to local recurrence was 89 months (mean: 69, range: 47-168). The 3- and 5-year actuarial local control (LC) rates were 68.9 and 55.7%, respectively. The 3- and 5-year overall survival rates were 88.6 and 81.1%, respectively. There was a trend toward worse LC with tumors treated with radiation doses ≤ 13 versus > 13 Gy. There was no radiation necrosis or second malignant tumors noted in our series. Conclusion  This report, one of the largest GKRS series for grade 2 meningiomas, demonstrates that GKRS is a safe and effective treatment modality for patients with grade 2 meningiomas with durable tumor control and minimal toxicity. Adjuvant GKRS could be considered as a reasonable treatment approach for patients with grade 2 meningiomas.

Parameters influencing local control of meningiomas treated with radiosurgery

To identify parameters that influence local control after stereotactic radiosurgery (SRS) for meningiomas we retrospectively analyzed all meningiomas treated with Gamma Knife SRS at our institution from 1991 to 2007. Endpoints were measured from the date of SRS and estimated using the Kaplan-Meier method; subgroups were compared with log-rank tests. Sex, performance status, age, SRS setting, radiation dose, grade, volume and location were evaluated with univariate and multivariate Cox proportional hazards analyses. Of 280 patients with 438 tumors, 264 patients with clinical follow-up and 406 tumors with imaging follow-up were analyzed (median follow-up: 75.9 months). Thirty-seven percent of the tumors had no tissue diagnosis, 32 % were benign (grade I), 12 % atypical (grade II), and 19 % malignant (grade III). Five-year freedom from progression (FFP) was 97 % for presumed meningiomas, 87 % for grade I tumors, 56 % for grade II tumors, and 47 % for grade III tumors (p < 0.0001). Five-year FFP probabilities for upfront SRS versus SRS at recurrence after surgery versus SRS at recurrence after RT were 97, 86, and 38 %, respectively (p < 0.0001). Univariate analysis revealed that higher grade, larger target volume (median diameter: 2.4 cm) and SRS setting were associated with poorer FFP. Only target volume and SRS setting remained significant on multivariate analysis. Local control of presumed and grade I meningiomas is excellent with Gamma Knife SRS, but is suboptimal with high-grade tumors as well as for those treated at recurrence after RT or of large volume.

Case-Based Review: meningioma

Meningioma is by far the most common primary intracranial tumor in adults. Treatment of meningioma is complex due to a tremendous amount of variability in tumor behavior. Many patients are incidentally found to have tumors that will remain asymptomatic throughout their lives. It is important to identify these patients so that they can be spared from potentially morbid interventions. On the other end of the spectrum, high-grade meningiomas can behave very aggressively. When treatment is necessary, surgical resection is the cornerstone of meningioma therapy. Studies spanning decades have demonstrated that extent of resection correlates with prognosis. Radiation therapy, either in the form of external beam radiation therapy or stereotactic radiosurgery, represents another important therapeutic tool that can be used in place of or as a supplement to surgery. There are no chemotherapeutic agents of proven efficacy against meningioma, and chemotherapy treatment is generally reserved for patients who have exhausted surgical and radiotherapy options. Ongoing and future studies will help to answer unresolved questions such as the optimum use of radiation in resected WHO grade II meningiomas and the efficacy of additional chemotherapy agents.