Purpose: To report long-term outcomes of 53 patients with vestibular schwannomas (VS) submitted to a single high-dose LINAC-based radiosurgery (SRS) in our institution.
Methods: 48 (92%) patients were evaluable for clinical and MRI response as well as late toxicity. At a median follow-up of 12 years (range 2-16 years), local control (LC), hearing capacity, trigeminal and facial nerve function, and toxicity were assessed. Hearing capacity was classified according to the Gardner-Robertson scale, where class I-II patients had "serviceable hearing."
Results: Median dose of SRS was 16.5 Gy (range 13-20 Gy) and median tumor volume 1.7 cm3 (range 0.09-7.4 cm3). 35 (73%) patients were treated with SRS alone, in the remaining 13 (27%) patients, SRS was performed as salvage therapy for recurrent or progressive tumors after previous microsurgery. Before SRS, 44 patients (92%) had hearing loss and 25 (52%) had "non-serviceable" hearing. Tumor extension, classified with Koos categories, was grade I-II in 27 (56%) and grade III-IV in 21 (44%) cases. LC was 100% and hearing preservation in "serviceable hearing" patients was 91%. 4 (11%) patients developed incomplete and intermittent ipsilateral facial nerve palsy which regressed in a median time of 6 months. Trigeminal toxicity was registered in 11 (23%) patients, reversible in 6 (13%) and permanent in 5 (10%). Only Koos tumor grade III-IV significantly influenced late toxicity (p = 0.01).
Conclusion: LC and hearing preservation after SRS were excellent. Toxicity proved acceptable. Although the median administered dose (16.5 Gy) was rather high, the only factor which significantly influenced late toxicity was Koos tumor grade III-IV.
Keywords: Hearing preservation; Koos tumor grade; Late toxicity; Radiosurgery; Vestibular schwannomas.