Repeat Stereotactic Radiosurgery (SRS) for Aggressive Vestibular Schwannoma That Failed Initial SRS

Introduction: There is limited literature on management options for aggressive vestibular schwannomas (VSs) that have progressed after initial stereotactic radiosurgery (SRS). This study reports a single-institution experience analyzing long-term outcomes after repeat SRS for progressed VS after initial SRS.

Methods: A retrospective review of patients treated between 1985-2022 was conducted. Twenty-six patients met the inclusion criteria. One (4%) patient had a subtotal resection for progression between the initial and repeat SRS. At the repeat SRS, the median margin dose was 11 Gy (IQR: 11-12), the median tumor volume was 2.0 cc (IQR: 1.3-4.3), and the median, mean cochlear dose was 4 Gy (IQR: 3.0-4.2). The median time from the initial SRS to repeat SRS was 65 months (IQR: 40-117).

Results: The median post-repeat SRS follow-up was 47 months (IQR: 21-101). Four (15%) patients had tumor progression after the repeat SRS. The 3-, 5-, and 10-year tumor control rates after the repeat SRS were 86%, 78%, and 78%, respectively. On multivariable Cox proportional analysis, tumor volume >3 cc (p=0.040, HR: 11.0, 95% CI: 1.12-108) at repeat SRS was significantly associated with tumor progression. After the repeat SRS, functional facial nerve (House-Brackmann grade 1 or 2, 17 (65%) patients) status and serviceable hearing (Gardner-Robertson grade 1 or 2, 5 (19%) patients) status were 100% preserved at the last follow-up. Improvement or stability of tinnitus, vestibulopathy, and CN V function after the repeat SRS was observed in 100%, 85%, and 88% of patients, respectively, at the last follow-up. One (4%) patient developed facial twitching and vestibulopathy in the absence of tumor growth 21 months after the repeat SRS and was successfully managed with bevacizumab.

Conclusion : Tumor control rates after repeat SRS for progressed VSs are high, and patients are likely to maintain their hearing and improve their clinical symptoms. Risks of adverse radiation effects remain low.