A systematic review 1 including 38 studies with a total of 7,383 subjects was abstracted in DARE. No study appeared to have a control group. There were 13 studies (n=903) of conservative management with radiologic follow-up, 9 studies (n=1,475) of gamma knife (GK) radiosurgery and 16 studies (n=5,005) of microsurgery. In the follow-up studies, the mean tumour growth was 1.87 mm/year (range: 0.35 to 3.22). 22% of the patients ultimately required intervention (microsurgery); the mean follow-up before intervention was 2.1 years. Hearing change was assessed in 3 studies (n=108). The mean pure-tone average deteriorated from 44.5 dB to 58.4 dB, and useful hearing was lost in 22 out of 60 patients. In patients undergoing GK radiosurgery, 56% of tumours regressed and 8% grew. Useful hearing after GK radiosurgery was preserved in 57% of the patients. Of 689 patients, 4.6% ultimately required microsurgery. Microsurgery resulted in total removal in 96% of patients; the tumour recurrence rate was 1.8%. Useful hearing was preserved in 36% of the patients.
For another systematic review 2 data were extracted from 19 articles. Success rates were adjusted using published data that 17% to 30% of vestibular schwannomas grow. The average reported success rate for stereotactic radiosurgery across all articles was 95.5%. When considering 17% or 30% natural growth without intervention, the adjusted success rates became 78.2% and 86.9% respectively. These rates were obtained by applying the natural history growth percentages to any tumors not reported to be growing before radiosurgical intervention. Success in the treatment of vestibular schwannomas with stereotactic radiosurgery is often defined as lack of further growth. Recent data on the natural growth history of vestibular schwannomas raise the question of whether this is the best definition of success. We have identified a lack of continuity regarding the reporting of success and emphasize the importance of the clarification of the success of radiosurgery to make informed decisions regarding the best treatment options for vestibular schwannoma.
Comment: The quality of evidence is downgraded by inconsistency (heterogeneity in interventions and outcomes) and by limitations in the review quality.
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