Parameters Associated with Treatment Success/failure in Vestibular Schwannoma After Microsurgery or Radiosurgery – a Large Comparative Study

Introduction: Stereotactic Radiosurgery (SRS) is a valid minimally-invasive treatment option in vestibular schwannoma (VS). However, it has been shown that not all VS respond positively to SRS (treatment success). Microsurgery (SURGERY)– on the other hand – remains the more invasive treatment option with a higher rate of peri-interventional morbidity. This study aims to identify clinical parameters linked to treatment success/failure in VS after SRS or SURGERY to provide data for a personalized-medicine-approach.

Methods: This is a retrospective two-center cohort study. Patients being treated for their VS between 2005 und 2014 were included. Previously treated VS and patients with Neurofibromatosis were excluded. Clinical state was reported by House and Brackmann (H&B) and Gardner-Robertson (G&R) scale (with H&B < 3 and G&R 1-2 considered as good outcome), and Recurrence-free-survival (RFS) was assessed radiographically by contrast-enhanced MR imaging. Treatment failure was defined as tumor recurrence/progression despite SRS or SURGERY.

Results: N=1’730 patients were included in this study. 35% were treated with SURGERY and 65% with SRS. The overall incidence of treatment failure was 10% after SRS and 7% after SURGERY. The incidence of treatment failure is higher in women with VS, when treated with SRS compared to men, although tumor characteristics were similar. After SRS, the rate of treatment failure was different in the different KOOS-subgroups with the lowest rate in KOOS I at 4%, 10% in KOOS II, the highest in KOOS III with 12% and 10% in KOOS IV. Lower rates of extent of resection (e.g. subtotal resection) was associated with treatment failure compared to gross total resection after SURGERY.

Conclusion : Higher initial tumor volume, female sex, and cystic morphology was associated with treatment failure in SRS – while residual tumor was associated with tumor recurrence (treatment failure) after surgical VS treatment. This large comparative study attempts to provide the framework for personalized decision-making in VS management.