Treatment of meningiomas    1.10

INTRODUCTION  Meningiomas are among the most frequent primary brain tumors.

Although most meningiomas are benign, their location in the central nervous system can cause serious morbidity or mortality. The approach to patients with meningioma and the prognosis following treatment depend upon the anatomic location of the lesion and tumor pathology.

OVERVIEW OF MANAGEMENT  The management of patients with meningioma requires a balance between definitive treatment of the tumor and avoidance of neurologic damage from the treatment. Patient-related factors (eg, presence or absence of symptoms, age, comorbidity), the location of the meningioma in relation to critical brain structures and regions, and the degree of atypia or malignancy of the tumor all are important factors in determining the optimal treatment.

With the widespread availability of magnetic resonance imaging (MRI) and computed tomography (CT), meningiomas are frequently being diagnosed while relatively small or as an incidental diagnosis with no associated symptoms. The natural history of such lesions may be very prolonged, and some tumors do not exhibit evidence of growth. Thus, active surveillance, with deferred treatment, may be an appropriate option.

For patients in whom active intervention is indicated, complete surgical resection is preferred when a meningioma is in an accessible location, since complete resection of the tumor and its dural attachment can be curative. Multiple advances in neurosurgery, including microsurgery, improved preoperative imaging, and intraoperative image-guided approaches, have extended the neurosurgeon's ability to resect lesions that were previously considered only partially resectable or unresectable, while minimizing damage to normal brain.

Subtotal resection can be combined with radiation therapy (RT) for less accessible lesions and for atypical and malignant meningiomas where the risk of recurrence is much higher. RT is used alone as the primary treatment for inaccessible lesions, when the risks of neurologic damage from surgery are too high. Newer conformal RT techniques, including stereotactic radiosurgery (SRS), fractionated stereotactic radiotherapy (SRT), intensity-modulated radiation therapy (IMRT), and proton radiotherapy, are important for the delivery of radiation to meningiomas that are in close proximity to critical structures such as the optic nerve, while minimizing radiation to normal brain structures.

ACTIVE SURVEILLANCE  Many meningiomas are discovered on a neuroimaging study (MRI, CT) obtained for minimal symptoms that or may not be related to the tumor. Such tumors may remain unchanged in size or grow only very slowly over prolonged periods. As a result, most patients with small asymptomatic meningiomas can be observed and resected or irradiated only if the tumors enlarge significantly or become symptomatic

The role of active surveillance was illustrated by a retrospective Japanese study of 1434 patients with meningioma, who were diagnosed between 1989 and 2003. In this series, 603 patients (42 percent) were asymptomatic and 351 of these were managed with observation. Of the 171 patients followed for more than one year, 31 were subsequently treated with either surgery or stereotactic radiosurgery (SRS), in most cases due to tumor growth. Among the 67 asymptomatic patients with follow-up of more than five years, 63 percent did not have evidence of tumor growth. Among the 213 asymptomatic patients treated surgically, morbidity occurred in 4 percent of those less than 70 years of age and in 9 percent of those ≥70 years. These data suggest that a large proportion of asymptomatic patients do not become symptomatic in the short-term, providing a rationale for active surveillance.

Our approach to the management of small, asymptomatic meningiomas is to reassess the patient with MRI or CT after three to six months. If the patient remains asymptomatic and there is no evidence of tumor growth, the patient can then be monitored with neuroimaging on an annual basis.

This approach is particularly suitable for older patients and those with significant comorbidity. For relatively healthy younger patients, there is a lower threshold for surgical intervention because of the expectation that tumor progression will inevitably require active intervention

SURGERY  Symptomatic meningiomas and asymptomatic tumors that are expanding, infiltrating, or associated with surrounding edema should be surgically resected if feasible. Surgery is also often recommended for asymptomatic meningiomas in younger patients who have accessible lesions. In this setting, early surgery may be preferred because surgical morbidity is lower than in an older population and there is an assumption that lesions will eventually progress.

Surgery is combined with radiation therapy (RT) for less accessible lesions and for atypical and malignant meningiomas (WHO grades II and III) where the risk of recurrence is high and negative surgical margins cannot be assured.

Extent of resection  Early observational studies demonstrated that complete resection, when feasible, was associated with significantly prolonged survival compared to partial resection. Complete surgical resection should include the dural attachment of the meningioma.

The Simpson grading system has been used to describe the extent of surgical resection

  • Grade 1, complete resection, including the dural attachment and any abnormal bone
  • Grade 2, complete resection, with coagulation of the dural attachment
  • Grade 3, complete resection, without resection or coagulation of the dural attachment
  • Grade 4, subtotal resection
  • Grade 5, tumor decompression only

Studies demonstrating the survival advantage from complete resection generally antedate the adjuvant use of radiation therapy (RT) with contemporary conformal techniques for patients with residual disease or with atypical/anaplastic meningiomas. The use of modern adjuvant RT to treat residual disease appears to yield results comparable to more aggressive surgery.

In contemporary practice, the goal of surgery is to achieve as extensive a resection as possible while minimizing neurologic deficits. The extent of resection varies depending upon the location of the tumor, whether there is imaging evidence of invasion, and the presurgical status of the patient (neurologic deficits, comorbidity).

  • Complete resection is usually attempted for tumors of the convexity, olfactory groove, anterior third of the sagittal sinus, and some tentorial and posterior fossa tumors.
  • Partial resection rather than complete resection may be more appropriate for less accessible tumors, such as those involving the posterior sagittal region or clivus. Residual tumor can be treated postoperatively with RT.
  • Biopsy alone or treatment without a tissue diagnosis may be needed for inaccessible tumors such as those involving the medial sphenoid wing or cavernous sinus. Definitive RT is the treatment of choice in these cases.

Because meningiomas are vascular tumors, preoperative embolization may be useful to increase resectability in carefully selected patients with skull base meningiomas. When indicated, this procedure can be performed the day prior to surgery.

Surgical morbidity  Postoperative neurologic deficits can be a direct complication of surgery. The reported incidence of such neurologic deficits ranges from 2 to 30 percent depending upon the location of the tumor and the extent of the resection. Cortical brain injury may occur if the arachnoid and pia are adherent to the tumor and there is disruption of the pial vasculature with subsequent cortical microinfarction. Cranial nerve deficits are a risk in surgery for skull base meningiomas, and intraoperative cranial nerve monitoring should be used for tumors located near the cranial nerves.

The reported overall surgical mortality has varied widely, reflecting differences in patient selection criteria as well as changes in surgical care. Factors associated with an increased mortality included poor preoperative clinical condition, brain compression from tumor, advanced age, incomplete tumor removal, and intracranial hematoma requiring evacuation

Older series indicated that the mortality was higher in elderly patients. More recent series, using contemporary neurosurgical techniques, have shown that surgery is feasible in carefully selected elderly patients. As an example, there was no perioperative mortality in a carefully selected series of 74 patients aged ≥80 years, and the incidence of postoperative complications was 9 percent

Perioperative medical management  In addition to neurologic deficits that are a direct consequence of surgery, common medical complications include seizures, deep venous thrombosis, pulmonary embolism, pneumonia, myocardial infarction, and arrhythmias.

Seizures  Seizures are a frequent presenting symptom of meningiomas and can also occur in the postoperative period.

Cerebral edema  Standard preoperative medications include corticosteroids to reduce brain edema. During the surgical procedure, mannitol and furosemide are administered and the arterial PCO2 is lowered to 30 mmHg to reduce intracranial pressure if the tumor is large or if significant brain retraction is anticipated. Corticosteroids are tapered postoperatively.

Deep venous thrombosis  Deep venous thrombosis (DVT) is especially problematic both because the thromboembolic risk in general is increased in patients undergoing brain surgery and because meningiomas can produce a hypercoagulable state. In one small series, for example, almost three-fourths of patients had evidence of postoperative DVT following surgery for intracranial meningioma' The hemostatic disorder in these patients resembles a chronic subclinical form of disseminated intravascular coagulation (DIC)

Prophylactic anticoagulation may lower the risk of thromboembolic events and should be considered in the postoperative period for all patients with brain tumors. Subcutaneous low-molecular-weight heparin is recommended postoperatively for patients requiring craniotomy for removal of a meningioma. In addition, pneumatic compression boots should be used until the patient is ambulatory.

RADIATION THERAPY  Radiation therapy (RT) has an important role in the management of meningiomas that have been subtotally resected or are unresectable because of their proximity to critical neurologic structures. RT is also used in some cases after presumed complete resection of atypical or malignant meningiomas, which otherwise have a high rate of local recurrence.

RT after subtotal resection  Although there are no randomized trials that assess the role of RT, observational studies have provided evidence that RT after a partial resection of a meningioma substantially improves progression-free survival compared to partial resection alone and may be as effective as complete resection. Whether this approach improves overall survival compared to using RT upon the development of a recurrence is unclear.

Accurate delineation of the residual tumor volume using contemporary imaging studies is important for optimal results with postoperative RT. This was illustrated by a retrospective analysis from the University of California at San Francisco, which included 140 patients who underwent a subtotal resection of an intracranial meningioma between 1967 and 1990 and were then treated with postoperative RT. For patients treated between 1967 and 1980, RT treatment volumes were based exclusively upon the surgeon's assessment of the site and volume of residual disease. From 1981 through 1990, RT treatment volumes incorporated information about residual tumor from CT and/or MRI. Among the 117 patients with benign meningiomas, the use of CT and/or MRI to plan the postoperative RT was associated with a significant improvement in the five-year progression-free survival (98 versus 77 percent).

Retrospective data from other groups also supports the role of RT in patients who have undergone subtotal resection of meningiomas

RT alone for nonresectable meningiomas  RT can also be effective in treating meningiomas that are not amenable to even a subtotal resection, providing excellent tumor control and avoiding the risks of surgery.

  • In one series, 101 patients with presumed benign skull base meningiomas were treated with fractionated radiation alone (66 cases) or after subtotal resection (35 patients) . Median follow up was five years. Local control rates for all patients were 95 percent at five years, and 92 percent at both 10 and 15 years.
  • In another retrospective series, 41 patients (with 42 meningiomas) were treated with RT without any surgery. RT consisted for stereotactic radiosurgery, stereotactic radiotherapy, or three-dimensional conformal RT in 22, 11, and 9 cases, respectively. At a median follow-up of five years, local control was achieved in 39 cases (93 percent).

High-grade meningiomas  Atypical (WHO grade II,  and malignant/anaplastic (WHO grade III) meningiomas have an increased frequency of recurrence even after gross total resection As an example, in a series of 936 intracranial meningiomas, the five-year recurrence rates after presumed complete resection for benign, atypical, and anaplastic meningiomas were 3, 38, and 78 percent, respectively

Although there are no randomized trials, the high risk of recurrence has led to the widespread use of postoperative RT in patients with WHO grade II or III meningiomas, even after a seemingly complete resection. In the largest series, the effectiveness of RT was assessed in 119 patients with atypical or malignant meningiomas treated at 10 European centers. RT (mean dose 55 Gy) was administered after the initial resection in 94 cases and for recurrence in the other 25. The overall and disease-free survival rates at 10 years were was 51 percent and 48 percent, respectively. On multivariate analysis a high mitotic rate was a poor prognostic factor.

Dosage and toxicity  When RT is used postoperatively to treat residual disease, a dose of 54 Gy in daily fractions of 1.8 to 2 Gy is generally used for benign meningiomas. Atypical and anaplastic meningiomas are treated with higher doses (typically 59.4 Gy).

The importance of the radiation dose is illustrated by a retrospective series of 140 patients with benign or malignant meningiomas, including an overlapping subset from the previously cited study. Among the 117 patients with benign meningiomas, those treated to doses >52 Gy had a better 10-year progression-free survival (93 versus 65 percent with ≤52 Gy). Similarly, among patients with malignant meningiomas, the five-year progression free survival was better with doses >54 Gy (63 versus 17 percent with doses ≤53 Gy).

Potential adverse effects of external beam radiation on the surrounding normal brain are rarely seen at fractionated doses of 54 Gy and are uncommon at doses up to 59.4 Gy.

RT technical advances  Technical advances that increase the dose of radiation to the meningioma while minimizing radiation to normal structures include stereotactic radiosurgery (SRS), stereotactic radiotherapy (SRT), and intensity-modulated radiation therapy (IMRT). Preliminary data indicate that proton beam therapy, where available, may also be useful in selected cases.

Stereotactic radiosurgery  Stereotactic radiosurgery (SRS) utilizes multiple convergent beams to deliver a high single dose of radiation to a radiographically discrete treatment volume, thereby minimizing injury to adjacent structures.

SRS is an alternative to surgery for small tumors in selected sites where complete excision is difficult or in patients at high risk for surgical resection. Although no randomized trials have been completed comparing SRS to surgery, the outcomes appear to be similar to surgery for small to medium-sized meningiomas. As an example, actuarial local control rates are 93 percent at five and 10 years for cavernous sinus meningiomas.

Stereotactic radiotherapy  Stereotactic radiotherapy (SRT) uses focused radiation in the same way as SRS but fractionates treatment over a series of sessions. Fractionation improves normal tissue tolerance of radiation, and SRT may be a reasonable alternative for patients with surgically inaccessible lesions, either as postoperative therapy following subtotal resection or to treat local recurrence

SRT may be particularly useful for patients with optic nerve sheath meningiomas, in whom surgery can cause postoperative blindness. In multiple small series, SRT resulted in preservation and/or improvement in vision in approximately 80 percent of cases. SRT also appears to be useful in those with small meningiomas of the skull base.

Intensity-modulated RT  Intensity-modulated RT (IMRT) is a technique that relies upon software and modification of standard linear accelerator output to vary the radiation intensity across each treatment field. IMRT may be particularly useful for patients with meningiomas when the target is juxtaposed to radiation-sensitive structures or has a particularly complex shape, such as those involving the skull base

ONCOLOGIC AND FUNCTIONAL OUTCOME  The results with surgery vary depending upon the location of the resected lesion, as well as the experience of the hospital and surgeon. Interpretation of results from large series also needs to consider the case mix.

Optimal therapy needs to be individualized, based upon the anatomic location of the tumor and patient-specific considerations. Results are discussed for two of the more common meningioma locations, convexity meningiomas, which usually can be managed with surgery alone, and skull base lesions, which often require a multidisciplinary approach.

Convexity meningiomas  Results with surgery primarily as a single modality are illustrated by a series of 163 patients with convexity meningiomas treated by a single surgeon over a 20-year period This cohort represented 22 percent of all meningiomas operated on during that period.

  • On pathologic examination, 88 percent of lesions were benign (WHO grade I), 10 percent were atypical (WHO grade II), and 2 percent were anaplastic (WHO grade III).
  • There were seven recurrences in the entire series (4 percent). For patients with WHO grade I, II, and III lesions, the five-year recurrence rates were 2, 27, and 50 percent, respectively, although these rates may increase with longer follow-up. The two benign meningiomas that recurred both had features of atypia and a high proliferative index.
  • There were no deaths within 30 days after surgery. The overall complication rate was 9 percent. Three patients had new neurologic deficits postoperatively, all of which represented worsening of motor weakness that was present preoperatively in patients with large (>4 cm) tumors.

Skull base meningiomas  The management of patients with skull base meningiomas is difficult because these lesions generally have an indolent history with only mild symptoms At the same time, radical surgery is associated with substantial morbidity because of the involvement of critical structures (vascular structures, cranial nerves, brainstem) and the high frequency of local recurrence.

The results of a combined modality approach are illustrated by a single surgeon series of 100 consecutive patients. Patients with minimal or no symptoms were initially managed with observation. Aggressive surgical resection was indicated for patients with a symptomatic tumor, for those with edema and mass effect, or progressive tumor enlargement. Conformal RT or stereotactic radiosurgery (SRS) was used for treatment of residual tumor following surgery or in those patients for whom surgical resection was contraindicated or refused.

Treatment included surgery in 72 cases, including 27 in which surgery was followed by radiation. Radiation alone was used in 13 cases and 15 patients were managed with observation. At a median follow-up of five years, only one patient had evidence of tumor progression. There were no treatment-related deaths, and serious complications from surgery were limited to hemiparesis, new cranial nerve palsy, and osteomyelitis (2.8, 2.8, and 1.4 percent of surgical cases, respectively).

The overall impact of diagnosis and treatment was studied in a single-surgeon series of 200 patients operated on for intracranial meningioma [47]. At a mean follow-up of 33 months, 36 patients had died within the first five years, including 18 due to the meningioma. Another eight patients died secondary to the meningioma after five years. Among the patients still living at the time of analysis, 80 percent were satisfied with their posttreatment quality of life, based upon a self-reported questionnaire.

The late impact of disease and treatment on neurocognitive function was studied at least one year after treatment in 89 patients who had been operated on for a grade I meningioma, including 22 who also received RT. Compared to matched healthy controls, patients had statistically significant impairment in several neurocognitive areas including executive functioning, verbal memory, information processing capacity, psychomotor speed, and working memory. Factors that appeared to partially account for these deficits include the use of anticonvulsants and the location of the tumor, but not the use of RT.

Neurocognitive impairment can be delayed after cranial irradiation and longer follow-up is required to definitively address this issue.

SURVEILLANCE AFTER INITIAL TREATMENT  Cranial imaging (preferably MRI) is used following initial treatment to monitor for evidence of recurrence or for progression of residual disease. There are no studies that define the optimal schedule for such imaging.

  • For asymptomatic or minimally symptomatic patients managed with active surveillance, our approach is to repeat the imaging procedure in three to six months and then annually if there is no evidence of progression.
  • For patients whose initial management consisted of surgery and/or RT, factors influencing the frequency of repeat imaging include the completeness of resection, the location of the tumor, and its pathology (WHO grade I versus grade II or III). In general, imaging should be repeated in the postoperative period, and then annually, so that any evidence of recurrent or progressive disease can be detected while the disease burden is relatively limited.

RECURRENT DISEASE  Most recurrences of meningioma are local or adjacent to a radiation treatment field. Metastases of cranial meningiomas to the spinal cord due to spreading through the cerebrospinal fluid are rare and are more frequently associated with atypical or malignant meningiomas. There are only isolated case reports of metastases outside the central nervous system

Surgery and RT for localized recurrences  Despite optimal therapy, some patients develop locally recurrent disease. For patients who recur locally after their initial treatment, additional surgery and/or RT (SRS, SRT, combined proton and photon RT) can sometimes provide effective therapy, and occasionally permit long-term overall and recurrence-free survival.

The principles underlying the use of surgery or radiation are similar to those for patients presenting de novo, but appropriate management requires a consideration of the effects of prior surgery and/or RT.

Systemic therapy  There is only limited experience with systemic therapy for the treatment of meningiomas, and most data are from observational studies. Systemic therapy has been used in small numbers of patients with recurrent, unresectable, and/or malignant meningiomas that are no longer controllable despite maximal surgery and RT.

Although a number of agents have been studied, none have an established role in prolonging progression-free or overall survival

Mifepristone  Epidemiologic evidence suggests that there is a link between progesterones and the progesterone receptor and the development or progression of meningiomas. Mifepristone is a progesterone and glucocorticoid receptor antagonist.

Preliminary studies indicated that mifepristone produced objective improvement in about 25 to 30 percent of patients with unresectable meningioma. However, a randomized, placebo-controlled trial conducted by the Eastern Cooperative Oncology Group (ECOG) in 160 patients with unresectable meningioma found there was no improvement in median time to progression with mifepristone compared to placebo (10 versus 12 months).

Hydroxyurea  Hydroxyurea induces apoptosis and inhibits meningioma cell growth in culture

Clinical experience with hydroxyurea consists of small series. In the two largest reports, there was only a modest degree of activity:

  • In one report, 16 patients with unresectable or recurrent benign meningiomas and four with atypical or malignant features. Although no objective antitumor responses were observed, 14 patients had stable disease for a median duration of 80 weeks.
  • In another series, stable disease was the best response to therapy in 18 of 20 patients with unresectable or recurrent meningioma who were progressing prior to therapy. Five patients progressed after a median follow-up of 176 weeks.

Interferon alfa-2b  In vitro, interferon alfa-2b (IFNa) inhibits the growth of meningioma cells exposed to mitotic stimuli, and preliminary reports suggested clinical activity.

The most extensive experience with IFNa comes from a prospective phase II study in which 35 patients with recurrent grade I intracranial meningiomas were treated with IFNa (10 million units subcutaneously every other day). All patients had received prior surgery and RT, and 34 had received prior systemic therapy. Although no objective responses were observed, 26 patients (74 percent) had stable disease for at least 12 weeks. Median overall survival was eight months.

The extent to which these results indicate clinical activity for IFNa is unclear, since grade I meningiomas are generally slow growing and multiple scans may be required to demonstrate significant changes in tumor size. Furthermore, the median overall survival of eight months suggests that this was a highly selected group of patients with a particularly poor prognosis.

Somatostatin analogs  Somatostatin receptors are present on most meningiomas. Case reports suggested that therapy targeted to this pathway might have therapeutic usefulness for patients with recurrent, unresectable meningiomas

A prospective pilot study treated 16 patients with a long-acting formulation of the somatostatin analog octreotide. All patients had recurrent, progressive meningioma and at least six months had passed since prior radiation therapy. All of the meningiomas expressed somatostatin receptors as demonstrated by a radiolabeled octreotide scan. Partial responses were observed in five patients (31 percent) and another five patients had stable disease. The median survival was eight months.

Another somatostatin analog, pasireotide (SOM230C), is currently being evaluated in a multicenter, phase II trial in patients with recurrent, progressive meningioma (NCT00859040).

SUMMARY AND RECOMMENDATIONS  The management of patients with meningioma requires a delicate balance between definitive treatment of the tumor and avoidance of neurologic damage from the treatment. Patient-related factors (eg, presence or absence of symptoms, age, comorbidity), the location of the meningioma in relation to critical brain structures and regions, and the degree of atypia or malignancy of the tumor all are important factors in determining the optimal approach to management.

  • For patients with small, asymptomatic meningiomas without edema or imaging evidence of invasion, we suggest careful observation without surgery or radiation therapy (RT)  Our approach is to repeat imaging in three to six months, and then annually thereafter. If there is subsequent evidence of tumor growth, we suggest active treatment with surgery and/or RT. For younger patients in good overall medical condition, early definitive intervention is an appropriate alternative to active surveillance.
  • Patients with meningiomas that are symptomatic, large, infiltrating, or associated with substantial edema require definitive treatment with surgery and/or RT. The choice of treatment (complete surgical resection, subtotal resection with or without RT, or RT alone) should be based upon the overall condition of the patient, the anatomic location of the tumor, the grade of the tumor (WHO grade I, II, or III), and the completeness of any surgical resection.
  • Perioperative management in patients undergoing surgical resection requires careful attention to prevent complications from cerebral edema, deep venous thrombosis, and seizures.