Frameless gamma knife stereotactic radiosurgery for over two hundred vestibular schwannoma patients - a single institution experience.

PURPOSE: Gamma Knife radiosurgery (GKRS) as definitive treatment for vestibular schwannomas (VS) provides high rates of tumor control. Traditionally, treatment immobilization necessitated a rigid stereotactic frame. The Gamma Knife Icon (Elekta AB) system enables frameless, mask-based immobilization. This study evaluates tumor control and hearing preservation after single- or five-fraction frameless GKRS for VS.

METHODS

We reviewed 206 patients with unilateral VS who underwent definitive single- or five-fraction GKRS with frameless immobilization between 2017 and 2024, ultimately including 170 patients with untreated VS. Radiographic follow-up was available for 112 patients, 40 of whom had both baseline and follow-up audiometric follow-up. Tumor control was assessed volumetrically on MRI and categorized as progressive, stable, partial response, complete response, or transient swelling. Serviceable hearing was defined as American Academy of Otolaryngology-Head and Neck Surgery class A or B. Kaplan-Meier methods estimated tumor control and and serviceable hearing preservation, and Cox regression evaluated associations with outcomes.

RESULTS

Among 112 patients with radiographic follow-up (median 2.3 years), 1- and 3-year tumor control rates were 97.1% and 93.7%. At last follow-up, 75.9% demonstrated stable disease or partial response, and 7 patients (6.3%) developed progressive disease. Of 76 patients with baseline serviceable hearing, 40 had audiometric follow-up; serviceable hearing preservation at 1 and 3 years was 71.1% and 33.8%, though 3-year data was limited. No factors were significantly associated with tumor control or hearing preservation.

CONCLUSIONS

Frameless GKRS for VS achieves acceptable tumor control that is comparable to historical frame-based series. These findings support the selective use of frameless GKRS, although warrant prospective studies with standardized radiologic and audiologic follow-up.