Population-Based Study of Stereotactic Radiosurgery or Fractionated Stereotactic Radiation Therapy for Vestibular Schwannoma: Long-Term Outcomes and Toxicities

Abstract

To examine long-term local control of vestibular schwannoma and side effects in patients treated with stereotactic radiosurgery (SRS) and fractionated stereotactic radiation therapy (SRT) in British Columbia. From August 1998 to May 2009, 207 patients were treated with radiation therapy (RT) at British Columbia Cancer Agency. 136 (66%) received SRS, and 71 (34%) received SRT. Dose prescriptions were 50Gy/25 fractions for SRT and 12Gy/1 fraction for SRS. Our multidisciplinary provincial neuro-stereotactic conference recommended SRT for tumors >3cm and for patients with serviceable hearing (Gardner-Robertson classes I and II). Median follow-up was 7.7years to the last MRI and 6.4years to the last clinical assessment. Local control for SRS versus SRT was 94% versus 87% at 5years and 90% versus 85% at 10years (P=.2). Five- and 10-year actuarial rates of RT-induced trigeminal nerve dysfunction were 25% and 25% after SRS, compared with 7% and 12% after SRT (P=.01). Five- and 10-year actuarial rates of RT-induced facial nerve dysfunction were 15% and 15% after SRS, versus 13% and 15% after SRT (P=.93). In the 49 patients with serviceable hearing at baseline who were treated with SRT, hearing preservation was 55% at 3years, 37% at 5years, and 29% at 7years. In multivariable analysis, better pretreatment ipsilateral pure tone average was significantly associated with hearing preservation (hazard ratio 1.03; 95% confidence interval 1.00-1.07; P=.04). Both SRS and SRT provided excellent long-term local control of vestibular schwannoma. Stereotactic radiosurgery was associated with higher rates of trigeminal nerve dysfunction. Even with a fractionated course, hearing preservation declined steadily with long-term audiometric follow-up.