Abstract
Stereotactic radiosurgery (SRS) has evolved as widely accepted treatment option for small-sized (Koos I up to II) vestibular schwannoma (VS). For larger tumors (prevalent Koos VI), microsurgery or combined treatment strategies are mostly recommended. However, in patients not suited for microsurgery, SRS might also be an alternative to balance tumor control, hearing preservation and adverse effects. The purpose of this analysis was to evaluate the efficacy and toxicity of SRS for VS with regard to different Koos grades. All patients with untreated VS who received SRS at our center were included. Outcome analysis included tumor control, preservation of serviceable hearing based on median pure tone averages (PTA), and procedure-related adverse events rated by the Common Terminology Criteria for Adverse Events (CTCAE; v4.03) classification. In total, 258 patients (median age 58 years, range 21–84) were identified with a mean follow-up of 52 months (range 3–228 months). Mean tumor volume was 1.8 ml (range 0.1–18.5). The mean marginal dose was 12.3 Gy ± 0.6 (range 11–13.5). The cohort was divided into two groups: A (Koos grades I and II, n = 186) and B (Koos grades III and IV, n = 72). The actuarial tumor control rate was 98% after 2 years and 90% after 5 and 10 years. Koos grading did not show a significant impact on tumor control (p = 0.632) or hearing preservation (p = 0.231). After SRS, 18 patients (7%) had new transient or permanent symptoms classified by the CTCAE. The actuarial rate of CTCAE-free survival was not related to Koos grading (p = 0.093). Based on this selected population of Koos grade III and IV VS without or with only mild symptoms from brainstem compression, SRS can be recommended as the primary therapy with the advantage of low morbidity and satisfactory tumor control. The overall hearing preservation rate and toxicity of SRS was influenced by age and cannot be predicted by tumor volume or Koos grading alone.
Highlights
Stereotactic radiosurgery (SRS) has evolved as widely accepted treatment option for small-sized (Koos I up to II) vestibular schwannoma (VS)
Between 1991 and 2012, patients were treated with a modified linear accelerator (LINAC), and from 2013 onwards patients were treated by robotic radiosurgery using the CyberknifeR system (CK)
Hearing loss up to a pure tone averages (PTA) level of dB was defined as serviceable hearing, PTA levels between dB and 90 dB as loss of serviceable hearing, and PTA levels of more than 90 dB were categorized as deafness according to the Gardner-Robertson Grades[9]
Summary
Stereotactic radiosurgery (SRS) has evolved as widely accepted treatment option for small-sized (Koos I up to II) vestibular schwannoma (VS). The actuarial rate of CTCAE-free survival was not related to Koos grading (p = 0.093) Based on this selected population of Koos grade III and IV VS without or with only mild symptoms from brainstem compression, SRS can be recommended as the primary therapy with the advantage of low morbidity and satisfactory tumor control. Due to the lack of alternative grading systems, the decision for treating patients with either surgery or radiosurgery is often based on the Koos grading system This scheme includes a qualitative estimation of both the size and localization of the tumor[6], it was developed mainly for neurosurgical purposes[7] and may not be adequate for predicting outcome and toxicity after SRS. We reviewed sporadic unilateral VS patient cases who underwent SRS with respect to the predictive value of the initial Koos grading alone or in conjunction with other potential predictive factors
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