MS-14 PATIENTS WITH RECURRENT ATYPICAL MENINGIOMA AFTER UPFRONT SURGICAL RESECTION SALVAGED WITH RADIOSURGERY REQUIRE MORE SALVAGE PROCEDURES THAN PATIENTS SALVAGED WITH CONVENTIONAL RADIATION

PURPOSE/OBJECTIVES: To determine the optimal salvage radiation treatment for recurrent atypical (WHO grade II) meningiomas after upfront surgery alone. METHODS: 35 patients (1997-2013) were treated at the Cleveland Clinic for histologically confirmed atypical meningiomas with upfront surgery alone and eventually required salvage radiation for recurrence. Patients were treated with either fractionated conventional radiation (RT) or stereotactic radiosurgery (SRS). Patients were grouped into a gross total resection group (GTR) or a subtotal resection group (STR) based on Simpson grade and operative notes. Local failure (LF) was defined as failure at or immediately adjacent to the resection cavity. Univariate analysis and Cox regression modeling was used for statistical analysis. Kaplan-Meier and log rank tests were used for survival analysis. RESULTS: Median age and follow up were 62 years (range 30-77) and 28 mo (range: 10-240), respectively. 23 patients received salvage RT and 12 had SRS. Median total dose for RT and SRS were 5940 cGy (range: 2500 - 6000) and 1400 cGy (range: 1000 - 1800), respectively. 10/23 patients (43.4%) experienced LF in the RT group and 8/12 patients (66.7%) experienced LF in the SRS group. Extent of initial resection (STR vs GTR, p = 0.12), number of pre-salvage radiation surgeries (1 vs 2 + , p = 0.79), and choice of salvage (RT vs SRS, p = 0.96) did not correlate with local relapse-free survival (LRFS). The number of additional salvage procedures after radiation (post-RT salvage) was significantly different (p = 0.02) between the RT (mean: 0.52 plus or minus 1.1) and SRS groups (mean: 1.33 plus or minus 1.3). OS was not significantly different between groups (p = 0.32). CONCLUSION: Patients initially salvaged with SRS were more likely to require additional salvage procedures, suggesting that the entire resection bed is at risk for recurrence and comprehensive radiation may be necessary. SRS can be used to salvage recurrence after salvage RT.