2011 Vestibular Schwannoma Koos Grade II International Study of Active Surveillance Versus Stereotactic Radiosurgery: The VISAS-K2 Study

INTRODUCTION: Affecting 2.93 per 100,000 in the U.S., vestibular schwannomas (VS) are benign tumors of the eighth nerve. The management includes observation, operative resection, and stereotactic radiosurgery (SRS). METHODS: A retrospective, multicentric analysis was conducted, focusing on patients with Koos grade II VS who either received SRS (SRS group) or were observed (observation group). To ensure comparability between groups, propensity score matching was employed, including factors such as demographic characteristics, tumor dimensions, and hearing assessments. The primary endpoints examined were tumor control, maintenance of serviceable hearing, and neurological outcomes. RESULTS: A total of 92 patients were equally matched across both cohorts, with a median follow-up of 37 months for the SRS group and 27.5 months for those observed. The SRS cohort exhibited superior tumor control over observation across 3, 5, and 8 years, achieving a 100% control rate versus 47.9%, 40.1%, and 34.3% for the observation group at these time intervals, respectively (P<0.001). Hearing preservation rates were comparable between the two groups throughout 3, 5, and 7 years (72.9% for SRS vs. 65.4% for observation at 3 years; P=0.86). Moreover, SRS management correlated with a lower incidence of vestibular dysfunction (OR=0.11, P=0.002), with no significant disparity in the deterioration of cranial nerve (CN) V or CN VII functions. Notably, the likelihood of experiencing any CN impairment was significantly diminished in the SRS cohort (OR=0.47, P=0.04). CONCLUSIONS: For patients with Koos grade II VS, SRS offers superior tumor control rate and a lower risk of cranial nerve dysfunction without sacrificing hearing preservation.