Excellent long-term local control of intracranial meningiomas with gamma knife radiosurgery in patients with neurofibromatosis type 2 (NF2)

Keywords: meningioma, gamma knife, neurofibromatosis Type 2, radiosurgery, outcome

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     Neurofibromatosis Type 2 (NF2) is characterized by the presence of intracranial and intraspinal meningiomas, vestibular schwannomas, and ependymomas.
     We report our experience treating a series of NF2-associated meningiomas with Gamma Knife radiosurgery (GK).
     Between January 1992 and December 2008, 16 consecutive patients (7 male, 9 female) with 58 meningiomas were treated with GK. The median age was 33 (range, 20-81). Thirty-three tumors (57%) involved the convexity or parasagittal/falx, 25 (43%) skull-based. None of the treated tumors had undergone previous surgery. Nine patients (56%) had more than 1 meningioma (range, 2-4) at presentation. During follow-up, 6 patients (38%) developed 26 (46%) new meningiomas, termed distant progression, requiring secondary treatments.
      The median tumor diameter was 2.3 cm and the median treatment volume (prescription isodose volume) was 3.6 cm3. The median prescription marginal dose was 16 Gy (range, 13-20), with a median maximum dose of 32 Gy (range, 24-40). The median radiographic and clinical follow-up periods were 62 and 86 months, respectively.
     Fifteen (93.8%) patients were alive at last follow-up (median overall survival not reached yet), with fifty-five tumors (94.8%) controlled (smaller or unchanged in size). Three tumors (5.2%) became larger at 36, 56 and 82 months, respectively, but were not re-treated; they belonged to the same patient who had 14 meningiomas treated over 7 sessions (in 12.7 years). There were no marginal failures. One minor complication was noted at 12 months, with hemi-body sensory changes that resolved. Two major radiation-related complications occurred at 1 and 3 months, including one patient who died following GK for a parasagittal meningioma. Radiation-related complication rates remained low overall, and were not associated with tumor volume, location, prescription dose, or chosen isodose level.
     This was a retrospective study.
     GK is an effective treatment for NF2 patients with meningiomas, with 5-year local control rate greater than 90% in our series.
     For NF2 patients who developed additional meningiomas and required repeat treatments elsewhere intracranially, secondary GK appeared safe and equally successful when compared with primary treatment. No high-grade meningioma or secondary non-meningioma malignancy were found as a result of GK radiation exposure.


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