Long Term Outcome of Vestibular Schwannoma Treatment in British Columbia

Background:Surgical removal remains the gold standard treatment for vestibular schwannomas (VS), but radiation therapy (RT) remains a viable alternative for small to medium-sized tumors with recent technological advances. Stereotactic radiosurgery (SRS) involves delivery of a high dose of radiation in a single treatment, while fractionated stereotactic radiotherapy (FSRT) involves 5 weeks of daily radiation treatment, with both utilizing a highly-targeted radiotherapy technique. Tumor control is excellent with any of the treatment approaches, with rates being reported at greater than 95% at 5 years.

Purpose: The aim of this study is to determine the long-term rates of local control and toxicity of patients with VS treated with SRS or FSRT at the British Columbia Cancer Agency, and with surgical resection at Vancouver General Hospital from 2001–2009.

Methods: 207 patients undergoing radiation therapy were analyzed and we have performed preliminary data collection and analysis on 294 patients who underwent surgical resection. We have analyzed patient demographics, clinical presentation, initial treatment (surgery, observation, radiation), and treatment outcomes including hearing tests, cranial nerve function, complications, and lesion recurrence. We then performed routine univariate and multivariate statistics, as well as logistic regression analyses.

Results: Baseline patient characteristics were comparable between the cohorts while patients with large lesions were more likely to receive surgery. Median follow up duration from start of RT was 7.7 years and 7.0 years following surgery. The overall cohort control rates for RT was 91.8% at 5 years, and 88.2% at 10 years, with slightly better control rate in patients undergoing SRS (93.8% versus 88.1% at 5 years, and 88.7 versus 86.5% at 10 years; p = 0.5). Surgery control rate was 91.3% at 5 years.

Patients who had RT required additional steroid treatment for symptom relief (12.1%). Most common complications following RT included communicating hydrocephalus (3.9%), bleeding from attachment of frame (1.5%), and delayed cyst formation (1.0%). Five-year overall survival was 94.0%±3.3% and 10-year overall survival was 83.0%±6.3%. Two (1.0%) of 207 patients died of complications from their disease, both 8 months after radiotherapy, one after SRS and the other after FSRT. Rates of cranial nerve toxicity following RT included trigeminal nerve dysfunction (8.7%) and facial nerve dysfunction (8.7%), disequilibrium (17.9%), and tinnitus (14.0%).

CSF leak (1.7%) and a post-operative resection bed hematoma with hydrocephalus (1.4%) were the most common complications following surgical excision of VS. One patient (0.3%) had a post-operative wound infection, and there were no mortalities. Cranial nerve dysfunction rates were (6.9%) for trigeminal nerve and (7.8%) for facial nerve.

Serviceable hearing preservation (Gardner Robertson I or II) was 36.7%±14.1% at 5 years and 28.7%±13.7% at 7 years following RT, and 38.9% at 5 years following surgery.

Conclusions: We hope our study will provide evidence of the long-term outcomes for patients with vestibular schwannoma tumors in British Columbia and give insight regarding treatment efficacy for different treatment modalities.