Introduction: Numerous studies have reported excellent control rates (>95%) with stereotactic radiosurgery (SRS) for vestibular schwannomas, but have not accounted for pretreatment tumor growth. The goal of this study was to determine the SRS control rate for growing vestibular schwannomas.
Methods: This retrospective single-institution study included all sporadic vestibular schwannomas treated primarily with Gamma Knife radiosurgery between 2002 -2014. Patients with < 2 years follow-up were excluded. Volumetric analysis was performed on the initial, treatment, and latest follow-up MR T1 post-contrast imaging, from which the pre- and post-treatment percent volume change was calculated. Radiographic and clinical control rates were calculated for both 'growing' and 'stable' groups, and compared using a Chi-sqaure test.
Results: 184 sporadic vestibular schwannomas were primarily treated with Gamma Knife SRS between 2002 and 2014. 97 cases were excluded due to insufficient follow-up information. The remaining 87 patients included 50 women, had a median age of 60.9 years, tumor volume of 0.78 cm2, and follow-up time of 4.25 years. Median dose prescription was 12 Gy to the 50% isodose line. Five patients required salvage treatment (4 surgical, 1 repeat Gamma Knife). The overall clinical (no salvage treatment required) and radiographic (no significant volume increase) control rates were 96% and 76%, respectively. Prior to SRS treatment, 34 patients had significant tumor growth (median increase 60% per year, median treatment volume 0.9cm3), 36 did not have significant growth (15% per year, 0.6 cm3), and 17 did not have interval pre-treatment imaging. The clinical control rate was 97% for both growing and stable tumors (median follow-up 3.3 and 4.5 years, respectively). Radiographic control rates were 68% and 81%, respectively (not significant).
Conclusions: In this small series, we did not see a significant difference in the clinical or radiographic control rates after SRS for growing versus stable vestibular schwannomas.
Patient Care: This research will improve patient care by helping clinicians to understand the optimal treatment modality for sporadic vestibular schwannomas.
Learning Objectives: By the conclusion of this session, participants should be able to: 1) Describe the control rates of SRS for vestibular schwannomas, 2) Describe the implications of pretreatment tumor growth on the effectiveness of SRS