Gamma Knife Radiosurgery For Recurrent Atypical Meningiomas

Keywords: meningioma, gamma knife, malignant meningioma, radiosurgery, outcome

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     Atypical meningiomas are characterized by frequent recurrences even after complete resection or adjuvant external-beam radiation therapy.  Repeated recurrences lead to deteriorate the patient’s performance status. 
     The purpose of this study is to assess the effectiveness of salvage treatment with gamma knife radiosurgery (GKS) for recurrent atypical meningiomas.
     We analyzed 8 patients with atypical meningiomas treated by GKS in our hospital since September 2002.  All patients had undergone periodic magnetic resonance (MR) imaging after GKS.  An additional GKS was performed when a new lesion or recurrence was found.  The median numbers of treated lesions and required GKS sessions in each patient were 5 (1-22) and 2 (1-5), respectively. 
     Tumor volumes in each lesion ranged 0.1-14.7 ml (mean; 1.9ml). The mean prescription dose delivered to the margin was 17 Gy (15-18 Gy). The Karnofsky Performance Status (KPS) scores at the first GKS ranged 50-100 (median; 80).
     The follow-up period was 11-46 (median; 34) months.  In 43 lesions which had been evaluated by MR imaging at least one time after GKS, local tumor control was achieved in 41 lesions (95%).  Progression-free survival at 12 and 24 months were estimated 75% and 50%, respectively.  In 38 lesions which were newly found in the follow-up MR images, 6 lesions (16%) had grown in the adjacent to the target volume at the prior GKS, whereas 32 lesions (84%) had distantly emerged.  As a result of an additional GKS for these new lesions, all patients but one (7/8) were not required a further operation.  Hyperintense area at the adjacent parenchyma on T2-weighted MR images enlarged in 3 lesions after GKS and caused neurological deterioration in one patient.  In 7 patients (88%), KPS scores at the latest follow-up examination were kept as same as those at the first GKS.
     This is a retrospective study.
     GKS for atypical meningiomas achieves a satisfactory outcome in the local tumor control. 
     Although repeated GKS may be required when a new lesion is detected, the patient’s performance status can be kept by the elaborate salvage treatment.


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