Preliminary Results Of Gamma Knife Radiosurgery For Optic Glioma: Report Of Two Cases

Keywords: gamma knife, vision, optic nerve, outcome, astrocytoma

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     Optic pathway/hypothalamic gliomas represent approximately 1% to 5% of brain tumor in pediatrics. Total excision, subtotal excision, subtotal excision followed by irradiation, radiation therapy (RT) alone, chemotherapy, and no treatment at all have been reported.
     We report the preliminary results of Gamma knife radiosurgery (GKRS) of optic gliomas in two children.
     We report on 2 pediatric patients (1 male and 1 female) treated for optic gliomas with GKRS in our institution between March 2005 and August 2005. Their ages were 10 and 16 years at presentation for GKRS. In all patients, partial resection had been performed. The histological diagnosis was confirmed as pilocytic astrocytoma in all cases. The location of the tumors involved optic chiasm in 1 patient and right optic nerve in 1 patient.
     The patients were planned using LGP 5.32 for Model C Gamma knife. Treatments were planned with the prescription of 11 Gy to 50% isodose for the chiasm glioma and 15 Gy to 50% isodose for the optic nerve glioma.
     The GKRS was well tolerated in all patients. The follow up periods were 50 and 55 months. All patients were alive during the follow-up period. Complete response with almost total disappearance of the tumors was observed in these two patients. During the follow-up period, none of the patients developed any endocrine dysfunction.
     This is a retrospective study.
     With the ability to deliver a high dose to the tumor while sparing normal brain tissue, especially the optic nerve, chiasm, and pituitary gland, GKRS should be the choice of treatment because every effort should be made to keep toxicity of radiation low.
     Complete response with almost total disappearance of the tumors was observed in our presented patients. However, the number of patients is too small and the follow-up period relatively too short to draw any definitive conclusion at this time. A larger number of patients and long-term follow-up is required for further evaluation of efficacy and potential side effects.


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