Impact of pretreatment growth on Tumor control for vestibular schwannomas following gamma knife

Objectives/Hypothesis: To determine if volumetric growth prior to gamma knife (GK) radiosurgery predicts long-term tumor control. Study Design: Retrospective cohort study. Methods: Sporadic vestibular schwannomas (VS) treated with GK between 2002 and 2014 at a single tertiary care center were identified. Patients were included if they had over 6 months of pretreatment observation and over 1.5 years of posttreatment follow-up. Volumetric tumor analysis was performed on T1 postcontrast imaging. Pretreatment and posttreatment volume change was calculated. Tumors with over 20% volume increase were classified as growing. Results: There were 62 patients included in this study; 48 had pretreatment growth and 14 had no pretreatment growth. Median tumor volume was 0.58 ± 1.8 cm ³ and median follow-up was 3.3 ± 2.0 years. For tumors with and without pretreatment growth, salvage treatment rates were 2% and 7% (P =.35), and posttreatment radiologic stability rates were 73% and 86%, respectively (P =.33). Median pretreatment growth was 27 ± 33% per year for tumors with posttreatment radiographic growth and 18 ± 26% per year for tumors without posttreatment radiographic growth (P =.99). Conclusions: Pretreatment growth was not associated with increased salvage treatment or posttreatment radiographic progression rates in VS following GK. Level of Evidence: 4 Laryngoscope, 129:743–747, 2019.