Radt-25. Recurrent Meningiomas Reirradiated With Large-Volume Pulsed-Reduced Dose Rate Radiotherapy: Long-Term Survival and Toxicity Outcomes

Meningiomas are the most common primary brain tumors in adults. Although local control is often achievable with surgical resection and radiation therapy, patients with recurrent disease treated with prior radiotherapy (RT) have few options for salvage treatment. We investigate retrospectively whether pulsed-reduced dose rate RT (PRDR) is effective and well-tolerated in a cohort with recurrent meningioma treated with prior radiotherapy. We retrospectively identified 26 patients with recurrent meningioma treated with PRDR from 2003 to 2025 at a single institution. Acute and late toxicities were graded based on CTCAE 5.0. Radiographic progression was assessed using RECIST criteria. Cumulative incidence method with death as a competing risk was used to analyze local recurrence. The Kaplan-Meier method and Cox proportional hazards models were used for progression free survival (PFS), overall survival (OS), univariate, and multivariate analyses. Median time between RT courses was 7.5 years. Median age and Karnofsky Performance Status at the time of PRDR were 68 years old and 90, respectively. Median PRDR dose was 54 Gy in 27 fractions (range 37.5-64 Gy, 15-33 fractions). Median planning treatment volume was 207.4 cm3. Seven patients (27%) received a boost of 4 to 6.6 Gy to gross disease. PFS at 6 months was 77% and median PFS was 20.5 months. Eleven patients (42%) had in-field failure with a median follow up of 18 months. Eleven patients (42%) were still alive at last follow up. Median OS was 33 months. Four patients (15%) experienced grade ≥ 3 acute or late toxicities. PRDR resulted in a manageable toxicity profile and achieved PFS for a cohort of patients with meningioma previously treated with RT. Notably, the median PFS observed in this study compares favorably to a recent phase II trial evaluating radiopharmaceutical therapy for refractory meningioma.