Gamma knife stereotactic radiosurgery for radiation-induced meningiomas.

BACKGROUND Radiation-induced meningiomas present a unique clinical dilemma given the fact that patients with these tumors have often received a prior full course of radiotherapy. As such, traditional radiotherapy is limited by lifetime tissue tolerances to radiation, leaving surgery and radiosurgery as attractive treatment options. OBJECTIVES To ascertain the safety and efficacy of Gamma Knife radiosurgery as a treatment for radiation-induced meningiomas. METHODS A retrospective chart review was conducted to identify patients who received Gamma Knife radiosurgery for a meningioma and met the criteria for this being a radiation-induced tumor. Serial imaging was used to determine the outcome of treatment and clinical notes used to assess for toxicity. RESULTS We present our series of 12 patients with radiation-induced meningiomas treated with Gamma Knife stereotactic radiosurgery over a 12-year period at our institution. With a median follow-up of 35 months, local control was 100%. Two patients experienced distant brain failure (>2 cm from previous radiosurgical volume). Two patients experienced posttreatment toxicity related to treatment-related edema. A review of data collected from the scientific literature suggests that tumor volume predicts for treatment failure of radiosurgery. CONCLUSIONS Gamma Knife radiosurgery is both a safe and effective treatment for radiation-induced meningiomas.