Stereotactic Radiosurgery of World Health Organization Grade II and III Intracranial Meningiomas

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1 Stereotactic Radiosurgery of World Health Organization Grade II and III Intracranial Meningiomas Treatment Results on the Basis of a 22-Year Experience Bruce E. Pollock, MD 1,2 ; Scott L. Stafford, MD 2 ; Michael J. Link, MD 1 ; Yolanda I. Garces, MD 2 ; and Robert L. Foote, MD 2 BACKGROUND: A study was undertaken to define the variables associated with tumor control and survival after single-session stereotactic radiosurgery (SRS) for patients with atypical and malignant intracranial meningiomas. METHODS: Fifty patients with World Health Organization (WHO) grade II (n ¼ 37) or grade III (n ¼ 13) meningiomas underwent SRS from 1990 to Most tumors were located in the falx/parasagittal region or cerebral convexities (n ¼ 35, 70%). Twenty patients (40%) had progressing tumors despite prior external beam radiation therapy (EBRT) (median dose, 54.0 grays [Gy]). The median treatment volume was 14.6 cm 3 ; the median tumor margin dose was 15.0 Gy. Seven patients (14%) received concurrent EBRT (median dose, 50.4 Gy). Follow-up (median, 38 months) was censored at last evaluation (n ¼ 28) or death (n ¼ 22). RESULTS: Tumor grade correlated with disease-specific survival (DSS) (hazard ratio [HR], 3.4; P ¼.008), local tumor control (HR, 2.4; P ¼.02), and progression-free survival (PFS) (HR, 2.6; P ¼.02) on univariate analysis, but not on multivariate analysis. Multivariate analysis showed that having failed EBRT and tumor volume >14.6 cm 3 were negative predictors of DSS and local control (HR, 3.0; P ¼.02 and HR, 4.4; P ¼.01; HR, 3.3; P ¼.001 and HR, 2.3; P ¼.02;, respectively). Having failed EBRT was a negative predictor of PFS (HR, 3.5; P ¼.002). Thirteen patients (26%) had radiation-related complications at a median of 6 months after radiosurgery. CONCLUSIONS: Tumor progression despite prior EBRT and larger tumor volume are negative predictors of tumor control and survival for patients having SRS for WHO grade II and III intracranial meningiomas. Cancer 2012;118: VC 2011 American Cancer Society. KEYWORDS: brain tumor, meningioma, stereotactic radiosurgery, external beam radiation therapy. INTRODUCTION Meningiomas are the most common primary brain tumor in adults. Although many meningiomas are incidentally discovered and may be observed with serial imaging, larger tumors and tumors located adjacent to the cranial nerves are frequently symptomatic, and tumor-directed therapy is required. Surgical resection remains the preferred treatment whenever total removal can be accomplished with acceptable morbidity. 1 However, the tumor recurrence or progression rate can be significant when patients are followed for long periods after surgery, 2-4 and the clinical outcome of patients correlates with the tumor histology in addition to the degree of resection. In 2000 and 2007, the World Health Organization (WHO) revised the pathologic grading of meningiomas using a combination of objective criteria (mitotic index) and subjective criteria. 5-8 This reclassification has resulted in a higher percentage of meningiomas being classified as atypical (WHO grade II). In the series of 936 meningiomas reported by Kallio et al, 9 <5% of tumors were classified as atypical (4.7%), 9 whereas Willis et al reviewed 314 meningiomas resected from 1994 to 2003 and noted that >20% of tumors met the WHO criteria of grade II (20.4%). 10 The percentage of patients having anaplastic meningiomas (WHO grade III) has remained relatively stable (approximately 1%-2%). 9,10 External beam radiation therapy (EBRT) is commonly used to reduce the incidence of tumor recurrence for patients with WHO grade II and III meningiomas Over the past 2 decades, stereotactic radiosurgery (SRS) 16 has been performed for an increasing number of patients with atypical or Corresponding author: Bruce E. Pollock, MD, Department of Neurological Surgery, Mayo Clinic, 200 First Street SW, Rochester, MN 55905; Fax: (507) ; pollock.bruce@mayo.edu 1 Department of Neurological Surgery, Mayo Clinic College of Medicine, Rochester, Minnesota; 2 Department of Radiation Oncology, Mayo Clinic College of Medicine, Rochester, Minnesota DOI: /cncr.26362, Received: February 23, 2011; Revised: April 29, 2011; Accepted: May 25, 2011, Published online July 19, 2011 in Wiley Online Library (wileyonlinelibrary.com) 1048 Cancer February 15, 2012

2 SRS for WHO II/III Meningiomas/Pollock et al anaplastic meningiomas as an alternative to EBRT In this study, we reviewed our 22-year experience to define factors associated with tumor control and survival after single-session SRS for patients with WHO grade II or III intracranial meningiomas. MATERIALS AND METHODS Study Population The institutional review board at the Mayo Clinic College of Medicine in Rochester, Minnesota approved all aspects of this study. In accordance with Minnesota state statutes, living patients were required to consent to review of their medical records. No patient refused research authorization. A prospectively maintained computer database was used to identify 602 patients with intracranial meningiomas having SRS at our institution between 1990 and Fifty-four patients (9%) had histologically confirmed WHO grade II (n ¼ 39) or grade III (n ¼ 15) tumors. 5,7 Four patients were lost to follow-up. The pre-srs history, imaging, treatment plans, and follow-up were obtained using the computer database for the remaining 50 patients. Four patients (8%) had radiation-induced meningiomas diagnosed at a median of 18 years (range, years) after EBRT for childhood leukemia (n ¼ 2), low-grade glioma (n ¼ 1), and fibrosarcoma (n ¼ 1). The patient characteristics are outlined in Table 1. Of note, 20 patients (40%) had enlarging tumors (WHO grade II, n ¼ 12; WHO grade III, n ¼ 8) despite having prior EBRT (median dose, 54.0 Gy). SRS Radiosurgery at our institution was performed with the Leksell Gamma Knife (Elekta Instruments, Norcross, Ga). Dose planning was performed using magnetic resonance imaging (MRI) in 48 patients (96%). Two patients (4%) could not undergo MRI imaging, and dose planning was performed using stereotactic computed tomography. Four patients (WHO grade II, n ¼ 3; WHO grade III, n ¼ 1) had multiple tumors (median, 2 tumors) treated at the time of their initial SRS. Multiple isocenters (median, 9) were typically used to irradiate the enhancing tumors. The median tumor volume was 14.6 cm 3 (range, cm 3 ). The median tumor margin dose was 15.0 grays (Gy; range, 9-20 Gy), and the median maximum radiation dose was 30.0 Gy (range, Gy). Four patients with WHO grade II tumors and 3 patients with WHO grade III tumors received concurrent EBRT (median dose, 50.4 Gy). Nine patients underwent repeat SRS at a median of 24 months (range, months) for tumor progression. Table 1. Patient Characteristics Factor WHO Grade II, n537 WHO Grade III, n513 Sex, M/F 19/18 8/5 Median age, y [range] 55 [23-83] 61 [26-79] Radiation-induced tumor 4 (11%) 0 Neurofibromatosis type II 1 (3%) 0 Prior surgery Number of prior resections, 1 [1-3] 1 [1-3] median [range] Time from last surgery to SRS, 2 [0.25-9] 2 [0.5-6] median y [range] Extent of resection last surgery GTR 12 (32%) 4 (31%) STR 25 (68%) 9 (69%) Prior EBRT 12 (32%) 8 (62%) Time from EBRT to SRS, 3 [2-9] 1 [0.5-6] median y [range] Tumor location Parasagittal/convexity 24 (65%) 11 (85%) Skull base/tentorium 13 (35%) 2 (15%) Multiple tumors 3 (8%) 1 (8%) Median maximum tumor diameter, mm [range] 35 [13-103] 39 [19-82] Abbreviations: EBRT, external beam radiation therapy; F, female; GTR, gross total resection; M, male; SRS, stereotactic radiosurgery; STR, subtotal resection; WHO, World Health Organization. The median tumor volume was 2.3 cm 3 (range, cm 3 ). The median tumor margin dose was 18.0 Gy (range, Gy), and the median maximum radiation dose was 31.2 Gy (range, Gy). Two patients underwent a third SRS 8 and 15 months after their second procedure. One patient had a tumor volume of 5.7 cm 3. The tumor margin dose was 15 Gy, and the maximum dose was 37.5 Gy. The second patient had a tumor volume of 1.7 cm 3. The tumor margin dose was 20.0 Gy, and the maximum radiation dose was 40.0 Gy. Overall, the 50 patients underwent a total of 61 SRS procedures to treat 71 tumors. Follow-up and Statistical Analysis MRI and clinical evaluations were typically obtained at 3, 6, and 12 months, and then yearly from the time of SRS. Follow-up was performed at either our institution or by the patient s local physician with follow-up imaging sent for our independent review. New neurological deficits occurring after SRS were recorded, and deficits were classified as minor (no change to the functional status of the patient) or major (impaired functional status). New neurologic deficits were considered radiation-related complications unless there was evidence of tumor progression causing the symptoms. Tumor size and regions of Cancer February 15,

3 Figure 1. Actuarial disease-specific survival after radiosurgery of patients with World Health Organization (WHO) grade II meningiomas (solid line) and WHO grade III meningiomas (dashed line) is shown. increased signal on long repetition time sequences were recorded on follow-up MRIs and compared with MRI performed on the day of SRS for evidence of tumor progression or adverse radiation-related effects. Progressive tumor enlargement >2 mm noted on sequential studies was considered tumor growth and coded as a local failure. New tumor formation adjacent to the irradiated tumor was coded as a marginal failure, and new tumor formation away from the irradiated tumor was coded as a distant failure. Follow-up (median, 38 months) was censored at last evaluation (n ¼ 28) or death (n ¼ 22). Disease-specific survival (DSS; death because of meningioma), local tumor control (progression of treated tumor), progression-free survival (PFS; local recurrence, marginal recurrence, and/or distant new tumor), and radiation-related complication rates were determined using the Kaplan-Meier method. Univariate testing was performed using the log-rank test on the following variables: tumor grade (WHO grade II vs WHO grade III), sex, tumor location (parasagittal/convexity vs skull-base/tentorium), patient age (60 vs >60 years), prior EBRT (yes vs no), concurrent EBRT (yes vs no), tumor margin radiation dose (15.0 vs >15 Gy), maximum radiation dose (30 vs >30 Gy), and tumor volume (14.6 vs >14.6 cm 3 ). Factors with a P value of.10 or less on univariate testing were placed into a Cox proportional hazards model. All statistical tests were 2 tailed, and statistical significance was determined by a P <.05. RESULTS Survival Twenty-two patients (44%) died at a median of 27 months (range, months) after SRS. Nineteen patients (38%) died of tumor progression. The DSS at 1 year and 5 years was 90% and 62%, respectively. Univariate analysis found tumor grade (hazard ratio [HR], 3.4; 95% confidence interval [CI], ; P ¼.008) to correlate with DSS. The 1-year and 5-year DSS for patients with WHO grade II meningiomas was 97% and 80%, respectively, compared with 69% and 27% for patients with WHO grade III meningiomas (Fig. 1). Other factors associated with a worse DSS on univariate analysis included having failed prior EBRT (HR, 3.2; 95% CI, ; P ¼.01) and tumor volume >14.6 cm 3 (HR, 5.2; 95% CI, ; P ¼.004) (Table 2). Multivariate analysis found that having failed prior EBRT (HR, 3.0; 95% CI, ; P ¼.02) and tumor volume >14.6 cm 3 (HR, 4.4; 95% CI, ; P ¼.01) were negative predictors of DSS (Fig. 2). The DSS of 19 patients (WHO grade II, n ¼ 18; WHO grade III ¼ 1) who had not undergone prior EBRT and who had tumor volumes Table 2. Analyses of Disease-Specific Survival, Progression-Free Survival, and Local Tumor Control Factor Univariate Analysis, HR, 95% CI (P) Multivariate Analysis, HR, 95% CI (P) DSS LC PFS DSS LC PFS Tumor grade 3.4, (.008) 2.4, (.02) 2.6, (.02) 2.1, (.13) 1.7, (.19) 1.4, (.40) Sex 0.6, (.36) 0.7, (.31) 0.8, (.51) NT NT NT Tumor location 1.4, (.59) 1.1, (.79) 1.5, (.35) NT NT NT Age 1.0, (.47) 1.0, (.26) 1.0, (.25) NT NT NT Prior EBRT 3.2, (.01) 3.1, (.002) 3.6, (.0009) 3.0, (.02) 3.3, (.001) 3.5, (.002) Concurrent EBRT 0.8, (.78) 0.5, (.29) 0.6, (.44) NT NT NT Margin dose 0.9, (.31) 0.9, (.46) 1.0, (.90) NT NT NT Maximum dose 1.0, (.49) 1.1, (.16) 1.1, (.22) NT NT NT Tumor volume 5.2, (.004) 2.1, (.04) 2.1, (.06) 4.4, (.01) 2.3, (.02) 2.0, (.08) Abbreviations: CI, confidence interval; DSS, disease-specific survival; EBRT, external beam radiation therapy; HR, hazard ratio; LC, local tumor control; NT, not tested; PFS, progression-free survival Cancer February 15, 2012

4 SRS for WHO II/III Meningiomas/Pollock et al Figure 2. (Top) Actuarial disease-specific survival (DSS) after radiosurgery for patients without prior external beam radiation therapy (EBRT) (solid line) is compared with patients with failed prior EBRT (dashed line). (Bottom) Actuarial DSS after radiosurgery for patients with tumors 14.6 cm 3 (solid line) is compared with patients with tumors >14.6 cm 3 (dashed line). Figure 3. (Top) Actuarial local tumor control (LC) after radiosurgery for patients without prior external beam radiation therapy (EBRT) (solid line) is compared with patients with failed prior EBRT (dashed line). (Bottom) Actuarial LC after radiosurgery for patients with tumors 14.6 cm 3 (solid line) is compared with patients with tumors >14.6 cm 3 (dashed line) cm 3 was 100% at 1 year and 89% at 5 years. The DSS of 11 patients (WHO grade II, n ¼ 5; WHO grade III, n ¼ 6) who had failed prior EBRT and had tumor volumes >14.6 cm 3 was 55% at 1 year and 15% at 5 years. Tumor Control and Additional Treatments Seventy-one tumors (WHO grade II, n ¼ 55; WHO grade III, n ¼ 16) were evaluated by MRI after SRS. Sixteen tumors (22%) were unchanged in size, 21 tumors (30%) were decreased in size, and 34 tumors (48%) showed local tumor progression. Local tumor control at 1 year and 5 years was 85% and 45%, respectively. Univariate analysis found that tumor grade (HR, 2.4; 95% CI, ; P ¼.02), having failed prior EBRT (HR, 3.1; 95% CI, ; P ¼.002), and tumor volume >14.6 cm 3 (HR, 2.1; 95% CI, ; P ¼.04) correlated with local control (Table 2). Multivariate analysis found that having failed prior EBRT (HR, 3.3; 95% CI, ; P ¼.001) and tumor volume >14.6 cm 3 (HR, 2.3; 95% CI, ; P ¼.02) were negative predictors of local control (Fig. 3). Tumor progression was noted in 15 patients (30%) away from the original irradiated tumor. Twelve patients had marginal tumor progression noted at a median of 15 months (range, 9-104) after SRS. Three patients had new tumor formation distant to the original tumor noted at 10, 22, and 147 months, respectively. The PFS at 1 year and 5 years was 76% and 40%, respectively. Univariate analysis found tumor grade (HR, 2.6; 95% CI, ; P ¼.02) and having failed prior EBRT (HR, 3.6; 95% CI, ; P ¼.0009) to correlate with PFS (Table 2). Cancer February 15,

5 Figure 4. Actuarial progression-free survival after radiosurgery for patients without prior external beam radiation therapy (EBRT) (solid line) is compared with patients with failed prior EBRT (dashed line). Multivariate analysis found that having failed prior EBRT (HR, 3.5; 95% CI, ; P ¼.002) was a negative predictor of PFS (Fig. 4). Nine of 12 patients having marginal tumor progression underwent either repeat SRS (n ¼ 7) or 2 additional SRS procedures (n ¼ 2). Two patients with distant tumor progression also underwent repeat SRS. Additional tumor resections were performed in 6 patients with either local (n ¼ 5) or distant tumor progression (n ¼ 1). Three patients underwent additional tumor resection and EBRT for either local (n ¼ 2) or marginal (n ¼ 1) tumor progression. Complications Thirteen patients (26%) developed radiation-related complications at a median of 6 months (range, 2-63 months) after SRS (n ¼ 12) or repeat SRS (n ¼ 1). Of these 13 patients, 5 had undergone prior EBRT, 2 underwent concurrent EBRT, and 6 had no radiation treatment other than SRS. Nine patients (18%) had major complications (hemiparesis, n ¼ 5; hemiparesis and increased seizures, n ¼ 4), and 4 patients (8%) had minor complications (single seizure controlled with medications, n ¼ 2; oculomotor nerve paresis, n ¼ 1; hypoglossal nerve paresis, n ¼ 1). The incidence of radiation-related complications after SRS was 21% at 1 year and 23% at 5 years. No tested factor correlated with radiation-related complications after SRS. DISCUSSION Patients with residual or recurrent WHO grade II or III intracranial meningiomas represent a management challenge, and the optimal treatment is not well defined. At initial presentation, patients with symptomatic or enlarging duralbased enhancing lesions are usually recommended to undergo complete resection whenever possible to relieve mass effect, minimize the chance of tumor recurrence, and allow pathologic review. Similar to the experience with WHO grade I meningiomas, the chance of tumor recurrence for patients with higher grade meningiomas is related to the degree of tumor removal. Goyal et al found a 10-year recurrence rate of 13% for patients having a gross total resection (GTR)ofanatypicalmeningiomacomparedwitha10-year recurrence rate of 83% for patients having a subtotal resection. 2 Patients with residual or recurrent WHO grade II meningiomas frequently receive EBRT to the imaging-defined tumor with a margin to improve local tumor control and minimize the chance of recurrence in the resection cavity. Pasquier and colleagues from the Rare Cancer Network reported 82 patients with WHO grade II meningiomas who received EBRT (mean dose, 54.6 Gy) after initial resection oratthetimeofrecurrence. 13 The 5-year PFS rate for these patients was 62%. Patient age >60 years and a high mitotic rate were associated with overall survival, whereas only high mitotic rate correlated with PFS. Survival and tumor control of WHO grade III meningiomas is poor despite aggressive surgical and radiation treatments. Rosenberg et al reviewed 13 patients with anaplastic meningiomas and reported a median time to recurrence of 9.6 months and a median survival of 3.4 years. 14 Kondziolka et al noted that 24 of 29 (83%) WHO grade III meningiomas progressed at a median of 15 months after SRS. 19 Our results support the contention that management of patients with WHO grade II or III meningiomas is difficult. We found that tumor progression after SRS was frequent, requiring additional resection, SRS, or EBRT, and that many patients die from their intracranial disease. Tumor grade correlated with DSS, local control, and PFS on univariate analysis, but multivariate analysis suggested that having failed prior EBRT and larger tumor volumes were also important negative predictors of survival and tumor control. The DSS of 19 patients, the majority of whom had WHO grade II tumors (n ¼ 18), who had not undergone prior EBRT with smaller tumors was 100% at 1 year and 89% at 5 years, compared with 55% at 1 year and 15% at 3 years for 11 patients who had failed prior EBRT and who had larger tumors. In addition, the radiationrelated complication rate was high in our series (26%), and the majority of complications adversely affected the patients normal day-to-day functioning. Although no tested variable correlated with radiation-related complications in our analysis, the large tumor volumes (median, 1052 Cancer February 15, 2012

6 SRS for WHO II/III Meningiomas/Pollock et al 14.6 cm 3 ) treated and the finding that > 1 = 2 of the patients had either prior EBRT (n ¼ 20) or concurrent EBRT (n ¼ 7) likely contributed to our high complication rate; however, the number of patients in this series was not large enough to detect any significant risk factors for radiationrelated complications. Moreover, tumor location has been noted to be a significant risk factor for radiation-related complications after meningioma SRS. Radiosurgery for meningiomas over the convexities or along the superior sagittal sinus have higher rates of radiation-related complications compared with tumors involving the skull base and tentorium. 22,23 The finding that 35 patients (70%) in our series had supratentorial tumors also made radiation-related complications after SRS in our series more common than typically quoted after meningioma SRS. This study has several weaknesses that constrain its findings and clinical application. First, the series is a retrospective review performed over 2 decades, and thus patient selection bias and lack of a standardized treatment regimen was unavoidable. Moreover, as our institution is a tertiary care center, many patients had received prior care elsewhere, and SRS was performed as the only reasonable treatment for patients with enlarging tumors after 1 or more craniotomies and EBRT. Therefore, the applicability of our results to patients being counseled after the diagnosis of an atypical or anaplastic meningioma is first established may be limited. Nonetheless, we did note our best outcomes in patients who had smaller tumor volumes treated and who had not received prior EBRT. Consequently, we make every attempt to perform a complete or near-complete resection whenever it is safe for patients with dural-based masses. If the histologic review determines that the meningioma has a more aggressive pathologic appearance, and it is known by early MRI that the patient has residual tumor, then SRS is performed within the first several months to minimize the chance of tumor progression. Second, the median radiation dose of patients who underwent EBRT before SRS was 54 Gy, which is less than typically recommended for patients with atypical or anaplastic meningiomas. The current Radiation Oncology Therapy Group phase 2 trial (RTOG-0539) prescribes 54 Gy to patients with a WHO grade II after GTR, but uses 60 Gy for patients after subtotal resection (STR) and for patients with recurrent atypical meningiomas. Third, although radiation doses were prescribed ranging from 9 to 20 Gy to the tumor margin, the majority of patients(64%)receivedbetween14and16gy,andsoa meaningful dose-response analysis was not possible. It has been suggested that higher radiation doses should be prescribed for patients with WHO grade II and III meningiomas compared with their benign meningiomas, but dose escalation in our patients was not usually considered because of the large tumor size as well as the finding that many patients had undergone prior EBRT. Fourth, our series does not permit a comparison of the relative effectiveness of SRS and EBRT for patients with recurrent or progressing WHO grade II or III meningiomas. A randomized trial comparing tumor control and patient outcomes for the different radiation techniques after STR or for patients with recurrent tumors would be needed to determine whether 1 approach is more efficacious. All the patients in our series had definable tumor by imaging, so this study provides no information on the need for adjuvant radiation to the surgical bed of patients with WHO grade II meningiomas after a GTR. Therefore, whereas most clinicians would recommend some form of adjuvant radiation after an STR of a WHO grade II meningioma, the need for postoperative EBRT after a GTR of a WHO grade II meningioma remains a topic of debate. Aghi and colleagues reported 108 patients having a GTR of atypical meningiomas from 1993 to The 5-year actuarial recurrence rate of patients not receiving adjunctive EBRT was 41% compared with 0% for patients receiving EBRT. Moreover, in this series patients with a tumor recurrence (n ¼ 30) had a 10-year DSS of 69% despite 22 patients having additional resection and all patients having either EBRT or SRS. However, the limited number of patients in the radiotherapy group (n ¼ 8) and the short follow-up of these patients (mean, 3.1 years) limit the power of their findings. Appropriately, the authors concluded that immediate postoperative EBRT of patients having a GTR of a WHO grade II meningioma should be investigated further in larger, prospective studies. Of note, 2 patients in our series having an imaging-confirmed GTR of a WHO grade II meningioma followed by EBRT and developed a tumor recurrence requiring SRS 18 and 41 months after the completion of EBRT. Alternatively, Choi et al discussed the long-term morbidity associated with EBRT of large brain volumes and argued that irradiation of the entire postoperative tumor bed may not be necessary for many patients after STR of atypical meningiomas. 17 They reported 25 patients having multisession SRS for either residual (n ¼ 15)orprogressive(n¼ 10) WHO grade II meningiomas. The DSS, local control, and PFS at 3 years were 90%, 74%, and 62%, respectively. In the subset of patients who had not received EBRT before SRS (n ¼ 20), 5 had tumor progression that was either local or regional requiring additional SRS, surgery, or EBRT. They recommended Cancer February 15,

7 close observation of patients after GTR of WHO grade II meningiomas and early SRS at the time of recurrence. Hopefully, the phase 2 trial by the European Organization for Research and Treatment of Cancer ( ) and the Radiation Therapy Oncology Group (0539) will provide prospective information on the effectiveness of upfront EBRT for patients with WHO grade II and III meningiomas. 24 On the basis of our experience, we advocate careful imaging follow-up and withholding of EBRT for patients with an imaging-confirmed GTR of a grade II meningioma. If a patient is found later to have a nodular tumor recurrence away from critical structures, then SRS is recommended. Conversely, if a patient has a diffuse tumor recurrence or the tumor is in direct contact with the anterior visual pathways, then EBRT is recommended. Conclusions Stereotactic radiosurgery is a useful treatment option for patients with recurrent or progressive WHO grade II and III intracranial meningiomas. A management strategy emphasizing early SRS for patients with definable tumor on postoperative imaging will likely improve tumor control and patient survival and minimize radiation-related complications for this difficult patient group. FUNDING SOURCES No specific funding was disclosed. CONFLICT OF INTEREST DISCLOSURES The authors made no disclosures. REFERENCES 1. Simpson D. The recurrence of intracranial meningiomas after surgical treatment. J Neurol Neurosurg Psychiatry. 1957;20: Goyal LK, Suh JK, Mohan DS, Prayson RA, Lee J, Barnett GH. Local control and overall survival in atypical meningioma: a retrospective study. Int J Radiat Oncol Biol Phys. 2000;46: Pollock BE, Stafford SL, Utter A, Giannini C, Schreiner SA. Stereotactic radiosurgery provides equivalent tumor control to a Simpson grade 1 resection for patients with smallto medium-sized meningiomas. Int J Radiat Oncol Biol Phys. 2003;55: Stafford SL, Perry A, Suman VJ, et al. 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