P11.38.A CYSTIC VESTIBULAR SCHWANNOMA - A SUBGROUP ANALYSIS FROM A COMPARATIVE STUDY BETWEEN RADIOSURGERY AND MICROSURGERY

Abstract

Abstract BACKGROUND Some vestibular schwannoma (VS), show cystic morphology. It is known that these cystic vestibular schwannomas (cVS) bear different surgical risk profile compared to non-cystic VS (ncVS) in surgical treatment. This study aims to analyze the management of cVS compared to ncVS in a dual center study of surgically (SURG) and radiosurgically (SRS) treated VS patients. MATERIAL AND METHODS This is a retrospective multi-center cohort study. Data was retrospectively collected from two large centers involved in the treatment of vestibular schwannomas for patients between 2005 und 2011 to enable long-term follow-up (FU). Tumor size was classified by Koos Classification. Previously treated VS and VS associated with Neurofibromatosis were excluded. Clinical state was reported by House and Brackmann (H&B) and Gardner-Robertson (G&R) scale (with H&B and G&R 1-2 considered as good outcome), and Recurrence-free-survival (RFS) was assessed radiographically by contrast-enhanced MR imaging. Data on VS-associated symptoms like trigeminal affection, tinnitus, and vertigo/imbalance were also collected. RESULTS The study population included N=901 patients, who were treated in both centers. N=559 (62%) patients were treated by SRS, and N=342 (38%) patients by SURGERY. N=55 (6%) of all patients showed cystic MR-morphology. These were more often treated by SURG (N=31/55, 58%) compared to ncVS (N=311/845, 37%) (p=0.002). Patients with cVS were indifferent in mean age compared to ncVS. The rate of women was higher in cVS (64%), compared to ncVS (55%) (p=0.001). The overall incidence of recurrence was 16% in cVS (8% in ncVS). Tumor control was worse in cVS treated by SRS (N=6/24, 25%) compared to SURGERY (N=3/32, 9%). When surgically treated, gross total resection (GTR) was achieved in 87% in cVS, whereas this rate was higher in non-cystic VS at 96% (p=0.001). The number of patients N=5/32 (16%) with postoperative relevant facial palsy (HB>2) was significantly higher in cVS (ncVS: N=28/310; 9%). CONCLUSION Tumor control in cVS is significantly worse in SRS compared to SURG and SRS-treated ncVS. However, when cVS is treated surgically, the rate of GTR is lower and the number of patients with relevant postoperative facial palsy higher compared to ncVS. Cystic morphology in VS poses a challenge in management (both SRS and SURG) compared to non-cystic tumors. Treatmend decision and patients' consultation should contemplate and address negative prognostic factor of cystic morphology in VS.