Meningioma

Meningiomas are typically benign, slowly growing tumors which arise from the tissues that surround the brain (the meninges). They can be cured by complete surgical removal, but in many cases this is not feasible due to inaccessible tumor location. Occasionally, meningiomas can grow aggressively, or even be frankly malignant.

Recurrence rates after surgery depend on the extent of tumor removal and length of followup after surgery. After complete removal, recurrence of benign meningioma within 5 years is unusual, but at 15 years recurrence rates may be as high as 32%. If tumor removal is incomplete, over one third of patients show tumor progression within 5 years, and at 15 years after surgery nearly all patients demonstrate tumor regrowth.

Meningiomas in certain areas of the brain can be completely and safely removed a large percentage of the time. However, tumors in difficult locations such as the base of the skull or meningiomas that invade important brain structures frequently cannot be completely removed. Surgical complications occur more commonly in these patients, with cranial nerve injuries, strokes and CSF leaks occurring with significant frequency. Overall surgical morbidity rates average 25%, and operative mortality averages approximately 7% in this group of patients.

Radiation therapy has been shown to decrease recurrence rates for patients with incompletely removed meningiomas, and may improve survival as well. However, an unavoidable side effect of radiotherapy is exposure of a small portion of surrounding healthy brain tissue to the full radiation dose given to the tumor. Radiosurgery offers the possibility of avoiding significant irradiation of adjacent brain tissue while still delivering sufficient radiation dose to prevent further tumor growth.

Excellent results have been obtained with Gamma Knife radiosurgery for benign meningiomas. Approximately 93% of patients achieve long-term tumor control, as measured by tumor reduction or stabilization on followup scans 5 to 10 years after radiosurgery. Complication rates for Gamma Knife radiosurgery for meningiomas average 4%, with no treatment-related mortality.

Since patients with aggressive or malignant meningiomas tend to have more infiltrative tumors, Gamma Knife radiosurgery is usually given in conjunction with external beam radiotherapy. Radiosurgery is delivered as a "boost" dose to the visible tumor volume on MRI seen after completion of radiation therapy. Radiosurgery also may be used to treat meningiomas which have recurred after conventional radiation therapy.

References

Kondziolka D et al: Long-Term Outcomes After Meningioma Radiosurgery: Physician and Patient Perspectives. J. Neurosurg. 91:44-50, 1999

Hudgins W et al: Gamma Knife Treatment of 100 Consecutive Meningiomas. Stereotactic and Functional Neurosurgery 66:121-128, 1996

Kondziolka D et al: Stereotactic Radiosurgery of Meningiomas. in Gamma Knife Brain Surgery. Prog Neurol Surg. Basel, Karger, 1998, vol 14, pp 104-113

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