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Multi -session cyberknife for patients with vestibular schwannomas: preliminary outcomes

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Author:
No author available
Journal Title:
Chinese Journal of Neurosurgery
Issue:
10
DOI:
10.3760/cma.j.issn.1001-2346.2011.10.003
Key Word:
听神经瘤;放射外科;射波刀;Vestibular schwannoma;Radiosurgery;Cyberknife

Abstract: Objective To evaluate the preliminary outcomes in patient with vestibular schwannomas treated using multi - session cyberknife radiosurgery and introduce personal experience in treatment planning.Methods From December 2007 to February 2010,29 patients with vestibular schwannomas,their tumor diameter was 11 ~47 mm,were treated by cyberknife in our center.Twenty -six patients were diagnosed by MRI and cyberknife were primary treatment modality for them.Three patients had residual tumor.Three patients with bilateral vestibular schwannomas was neurofibromatosis Type 2.The tumor volume ranged from 0.3 to 36.0 cm3 ( mean,13.2 ±4.7 cm3 ),17 of them was more than 10 cm3 in volume.The radiation dose prescribed to the tumor margin of two giant tumors was 22 Gy and 22.8 Gy respectively in 4 fractions,the tumor margin dose of three small tumors was 16.8 Gy,17.4 Gy and 17.4 Gy respectively in 2 fractions.The margin dose of the rest 24 tumors ranged from 15.0 Gy to 21.0 Gy (mean,19.2 Gy) in 3 fractions.In treatment planning process,the author selected 65% to 70% isodose line to cover the tumor margin and the beam number was controlled between 150 and 200 to make the treatment planning more conformal and more higher dose volume within tumors.The mean duration of follow up was 21 months(range:14 - 38 months).Results One patient (77 years old) with giant tumor was deceased at 10 months post cyberkinfe because tumor swelling and medical condition,the rest 28 patients had normal life.Thirteen (92%) of 14 patients with serviceable hearing before cyberknife preserved serviceable hearing after cyberknife.One patient with non - serviceable hearing had improvement hearing at 1 year and recovered serviceable hearing at 2 year after cyberknife.Six patients developed temporary facial numbness and improved later.One patient with large residual tumor developed slight facial palsy at 12 months post cyberknife and recovered 5 month later.Three patients ( 10% ) developed hydrocephalus at about 12 months post cyberknife and 2 of them underwent a ventriculoperitoneal shunt.One patient with both vestibular and trigeminal schwannomas developed brain stem edema at 9 months because of irradiating two tumors at same time and some area of higher irradiation dose within brain stem.The edema disappeared 3 months later after administration of mannitol and dexamethasone.In 28 patients alive,tumor volume decreased more than 50% in 6 patients,decreased more than 20% in 15 patients.Seven tumors kept stable.In this ~ries tumor control rate was 96% (28/29).Conclusion Multi -session cyberknffe is an effective treatment for patient with small - and medium- sized vestibular schwannomas,and some patients with large vestibular schwannomas,who had contraindications for open surgery,but long- term follow-up is needed.

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