Reporting success rates in the treatment of vestibular schwannomas: are we accounting for the natural history?

Stereotactic radiosurgery is generally accepted as one of the best treatment options for vestibular schwannomas. We question whether growth control is an accurate measure of success in vestibular schwannoma treatment. We aim to clarify the success rate of stereotactic radiosurgery and adjust the reported results to the benign natural history of untreated tumors. All articles were taken from a PubMed search of the English literature from the years 2000-2011. Inclusion criteria were articles containing the number of patients treated, radiation technique, average tumor size, follow-up time, and percentage of tumors growing during follow-up. 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.