195 Vestibular Schwannoma Koos Grade I International Study of Active Surveillance Versus Stereotactic Radiosurgery: the VISAS-K1 Study

INTRODUCTION: The appropriate management of Koos grade I vestibular schwannomas (VS) remains controversial. METHODS: In a multicenter study, this report gathered and analyzed data retrospectively on Koos grade I VS patients who underwent SRS (SRS group) or were observed (observation group). Propensity score matching was utilized to equilibrate demographics, tumor size, and audiometric data across groups. The outcome analyzed included tumor control, preservation of serviceable hearing (SHP), and neurological function. RESULTS: The study matched 142 patients, providing a median follow-up period of 36 months. SRS significantly enhanced tumor control compared to observation, with a 100% control rate at both 5- and 8-year marks in the SRS group versus 49.7% and 33% in the observation group at the same time intervals, respectively (P<0.001). SHP outcomes between groups showed no significant difference at 5 and 8 years, ensuring a comparable quality of auditory function (SRS 70.1% vs. observation 53.4% at 5 years; P=0.33). Furthermore, SRS was associated with a reduced likelihood of tinnitus (OR=0.46, P=0.04), vestibular dysfunction (OR=0.17, P=0.002), and overall cranial nerve dysfunction (OR=0.49, P=0.03) at last follow up. CONCLUSIONS: SRS management of Koos grade I VS patients was associated with superior tumor control and reduced odds for dysfunction of various cranial nerves, while not compromising hearing preservation compared to observation. These findings support the safety and efficacy of SRS as a potential management modality for this patient population.