Introduction: To evaluate long-term treatment response and toxicities among vestibular schwannoma (VS) patients treated with hypofractionated stereotactic radiotherapy (HSRT).
Methods: A total of 446 patients with VS were treated at our institution between 1995-2007. HSRT was 25Gy/5 fractions.Treatment failure was defined as patients requiring salvage microsurgery. Post-treatment clinical symptoms or increases in baseline tumor volume (BTV) were noted. Audiometric analysis using Gardner Robertson (GR) scale assessed hearing and stratified as serviceable hearing (GR 1-2) or non-serviceable hearing (GR 3-5).
Results: Median follow up was 70 months. Overall 14(3.1%) patients experienced treatment failure. At last follow up, 29(6.5%) patients had new/progressive symptoms. Median BTV was 0.9cm3, with significant differences in BTV among patients with (0.3cm3) and without (1.2cm3) treatment failure (P < .001). Patients with new/progressive symptoms had the greatest median BTV at 4.7cm3 (P < .001).
Pre-treatment CNVII and CNVIII symptoms were present in 8% and 98% of all patients, respectively. 16(4%) had facial weakness and 32% improved. 211(47%) presented with imbalance and 12% improved. Regarding post-treatment symptoms, 43(10%) reported CNVII symptoms (53% transient) and 42(9%) reported CNVIII symptoms (50% transient).
234 patients had evaluable audiograms. Median baseline and post-treatment GR scores were 2 and 3, respectively, indicating a significant trend from serviceable to non-serviceable hearing (P < .001). Among 156 patients with serviceable hearing at baseline, 52% had a decline to non-serviceable hearing at last follow up.
One possible secondary malignancy and two HSRT-induced brainstem injuries were noted. 11 patients developed hydrocephalus.
Conclusions: HSRT is an effective option with treatment success in 97% and an acceptable toxicity profile. ~50% of patients with serviceable hearing at baseline maintain hearing function. Smaller median BTV was associated with increased risk of treatment failure and larger median BTV is more likely to cause clinical/radiologic progression. 50% of symptoms are transient and ~75% occur in patients with treatment success.
Patient Care: Highlight the need for improved methods to differentiate treatment effect and tumor progression among patients treated with HSRT for VS. Provide an alternative treatment scheme for management of VS.
Learning Objectives: By conclusion of this session, participants should be able to understand: (1) Long-term treatment response and outcomes for patients treated with a hypofractionated stereotactic radiotherapy (2) An alternative approach to single-fraction radiosurgery in the non-microsurgical management of vestibular schwannoma with the aim to reduce toxicities.