Gamma knife radiosurgery inhibit progression of vestibular schwannoma with pre-treatment evidence of growth-a retrospective long term follow up study

Keywords: vestibular schwannoma, radiosurgery, gamma knife, natural history, outcome

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     Gamma knife radiosurgery (GKRS) has for the last decades been an established alternative treatment for patients with vestibular schwannoma (VS). Studies of patients treated with GKRS for VS show tumor control (TC) rate in 90-97%. Epidemiological studies have shown that a large proportion of the VS are stationary when followed conservatively with repeated magnetic resonance images (MRI). The implication of these results could be that most VS are in no need for intervention. A major drawback with many of the existing studies is short follow up times.
     This study will investigate the long-term effect of GKRS on VS and evaluate the chance of growth inhibition after treatment of VS with pre-treatment evidence of growth.
     We reviewed a cohort of 128 patients, 62 men and 66 women, with VS who had consecutively been treated with GKRS at Karolinska University hospital between 1997-2003.
     Patients previously treated for VS, patients from abroad and patients with neurofibromatosis were excluded from the study. Mean age at time of treatment was 64 years (23-89). Patients were followed clinically for a median time of 96 months (11-165) and radiologically for 84 months (5-170). 5 patients were lost to follow up. 4 patients underwent GKRS for a second time. 6 patients had microneurosurgery due to progressive tumor growth.
     TC was achieved in 92% of patients after GKRS. Pre-treatment growth of VS was not correlated to rate of TC, strongly indicating that GKRS inhibit further growth of VS. 12 patients had loss of TC, 10 were re-treated either with surgery (6 patients) or with GKRS (4 patients). New treatment with surgery or GKRS was performed in median in 49 months from the first treatment. No correlation was noted between tumor size, age or gender of the patients and tumor control rate. 3% had trigeminal symptoms and 4% of the patients had facial nerve palsy after treatment.
     This was a retrospective study. 
     This study concludes excellent tumor control rate in patients with VS treated with GKRS in long time follow up. 
     The tumor control results are not dependent on the pre-treatment growth, or volume of the tumor.


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