ESTRO 2025 - Abstract Book

S685

Clinical - CNS

ESTRO 2025

vestibular and trigeminal symptoms are also critical objectives. This study evaluates the efficacy of Gamma Knife (GK) SRS in the treatment of sporadic unilateral VS.

Material/Methods: We included patients with unilateral sporadic VS treated with GK SRS at our center between 2012 and 2019. All patients had pre- and postoperative T1-weighted contrast-enhanced magnetic resonance imaging (MRI) available for analysis. Tumor volumes measured at the last follow-up (FUP) MRI were compared to baseline volumes. A minimum FUP of 3 years was required. Hearing function was assessed by audiograms, while facial nerve function and vestibular and trigeminal symptoms were evaluated using the House-Brackmann scale (HBS) and CTCAE 5.0 scale, respectively. A retrospective observational analysis was conducted. Results: A total of 71 patients were included in the analysis. Median FUP was 67 months (range 36-122 months) and median age at GK was 59 years (range 29-80 years). The median dose delivered was 12.5 Gy (range 12-13 Gy) at the 50% isodose. Fifty-five (78%) of patients had GK as exclusive treatment, while 16 patients (22%) had SRS after surgery (7 as adjuvant therapy and 9 for recurrence). The median tumor volume at GK was 2.16 cc (range 0.09-7.64 cc) and reduced to 1.4 cc (range 0.07-5.19 cc) at the last MRI. In 60 patients (85%), tumor volume decreased with an average reduction of 54% (range 15-95%). Four tumors remained stable, and seven increased in size without needing further intervention. Regarding symptoms, 38% of patients with initial complete hearing loss (8/21) experienced partial recovery. Hearing remained stable in 72%, and mild loss occurred in 1 out of 4 patients with preserved hearing at baseline. Tinnitus resolved in 79% of cases (15/19), and dizziness disappeared in 95% (21/22). Facial nerve function improved in three patients with initial deficits, while three new facial nerve deficits appeared in previously surgically treated patients (HB grades 2-4). Finally, 3 out of 4 patients with trigeminal symptoms had complete recovery (Table 1).

Conclusion: Our analysis supports GK SRS as a safe and effective treatment for sporadic unilateral VS, achieving good local control and managing symptoms effectively.

Keywords: Radiosurgery, benign tumors