Journal Article

Treatment Outcomes and Dose Rate Effects Following Gamma Knife Stereotactic Radiosurgery for Vestibular Schwannomas

Wu, Cheng-Chia, Wang, Tony J C, Lesser, Jeraldine, Sisti, Michael B, Smith, Deborah Ruth, Wuu, Yen-Ruh, Horan, Maryellen, Black, Paul J, Isaacson, Steven R, Saadatmand, Heva Jasmine

2019

Overview

Abstract BACKGROUND Gamma Knife radiosurgery (GKRS; Elekta AB) remains a well-established treatment modality for vestibular schwannomas. Despite highly effective tumor control, further research is needed toward optimizing long-term functional outcomes. Whereas dose-rate effects may impact post-treatment toxicities given tissue dose-response relationships, potential effects remain largely unexplored. OBJECTIVE To evaluate treatment outcomes and potential dose-rate effects following definitive GKRS for vestibular schwannomas. METHODS We retrospectively reviewed 419 patients treated at our institution between 1998 and 2015, characterizing baseline demographics, pretreatment symptoms, and GKRS parameters. The cohort was divided into 2 dose-rate groups based on the median value (2.675 Gy/min). Outcomes included clinical tumor control, radiographic progression-free survival, serviceable hearing preservation, hearing loss, and facial nerve dysfunction (FND). Prognostic factors were assessed using Cox regression. RESULTS The study cohort included 227 patients with available follow-up. Following GKRS 2-yr and 4-yr clinical tumor control rates were 98% (95% CI: 95.6%-100%) and 96% (95% CI: 91.4%-99.6%), respectively. Among 177 patients with available radiographic follow-up, 2-yr and 4-yr radiographic progression-free survival rates were 97% (95% CI: 94.0%-100.0%) and 88% (95% CI: 81.2%-95.0%). The serviceable hearing preservation rate was 72.2% among patients with baseline Gardner-Robertson class I/II hearing and post-treatment audiological evaluations. Most patients experienced effective relief from prior headaches (94.7%), tinnitus (83.7%), balance issues (62.7%), FND (90.0%), and trigeminal nerve dysfunction (79.2%), but not hearing loss (1.0%). Whereas GKRS provided effective tumor control independently of dose rate, GKRS patients exposed to lower dose rates experienced significantly better freedom from post-treatment hearing loss and FND (P = .044). CONCLUSION Whereas GKRS provides excellent tumor control and effective symptomatic relief for vestibular schwannomas, dose-rate effects may impact post-treatment functional outcomes. Further research remains warranted.

• Publisher: Oxford University Press,Copyright by the Congress of Neurological Surgeons,Wolters Kluwer Health, Inc
• Subject: Adult / Aged / Aged, 80 and over / Brain cancer / Care and treatment / Clinical outcomes / Cohort Studies / Female / Follow-Up Studies / Hearing - physiology / Hearing - radiation effects / Hearing loss / Hearing Loss - diagnostic imaging / Hearing Loss - etiology / Hearing Loss - prevention & control / Hearing Tests - trends / Humans / Male / Medical prognosis / Medical research / Medicine, Experimental / Middle Aged / Neuroma, Acoustic - diagnostic imaging / Neuroma, Acoustic - radiotherapy / Neurosurgery / Patient outcomes / Radiation / Radiation Dosage / Radiosurgery / Radiosurgery - adverse effects / Radiosurgery - trends / Research—Human—Clinical Studies / Retrospective Studies / Surgery / Treatment Outcome / Tumors