Outcomes of Stereotactic Radiosurgery and Stereotactic Radiotherapy for the Treatment of Vestibular Schwannoma

Introduction: Vestibular schwannoma (VS) is a benign tumor derived from Schwann cells typically in association with CN VIII. Common morbidities of these characteristically slow-growing lesions include hearing loss and facial nerve damage. Treatment options include observation, surgical resection, stereotactic radiosurgery (SRS), and stereotactic radiotherapy (SRT). In this study, we assess the outcomes of patients with VS treated with either SRS or SRT. Methods: Patients receiving SRS or SRT for vestibular schwannoma between 1996 and 2009 were reviewed. Inclusion criteria were: (1) histopathologically confirmed vestibular schwannoma, (2) SRT or SRS performed at UCLA Ronald Reagan Medical Center, and (3) functional hearing and/or tumor size assessed pre- and post-SRT or SRS. Functional hearing was categorized as full, partial, or none, with partial being defined as ability to use the phone with the affected ear. Tumor control was categorized as increased in size, stable, or decreased, with a change of greater than 2 mm required to be considered increased or decreased. Results: Fifty-four patients met all of the inclusion criteria. Of these, 46 received SRT and 8 received SRS. Twenty-eight (52%) were male and 26 (48%) were female. The average age at SRT or SRS procedure was 55 years (range, 23–83 years) and average radiation dose for SRT was 180 cGy to the 90% IDL over an average of 30 fractions and for SRS was 1263 cGy (range, 1200–1400 cGy). Patients had an average radiological follow-up of 44 months and average clinical follow-up of 36 months. Overall, 94% of patients had either stable or decreased tumor size on final radiologic follow-up, and 86% had stable or improved functional hearing on final clinical follow-up. SRT was associated with a lower rate of tumor size increase following treatment relative to SRS (6% vs. 25%, respectively; P = 0.054). Similarly, SRT was associated with fewer adverse functional hearing outcomes relative to SRS (11% vs. 25%, respectively, P = 0.296). Conclusions: Our data show good tumor control over time and preservation of functional hearing with SRS and SRT. Furthermore, SRT was associated with superior tumor control and functional hearing results relative to SRS. Further research will be needed to determine optimal use of SRT and SRS for treatment of VS.