RTRB-09SALVAGE STEREOTACTIC RADIOSURGERY TO RECURRENT GLIOBLASTOMA MULTIFORME FOLLOWING PRIOR RADIOTHERAPY

BACKGROUND: Due to the poor prognosis of glioblastoma multiforme (GBM) and high recurrence rates, salvage stereotactic radiosurgery (SRS) may be an effective treatment option given its ability to deliver a high dose of radiation within a small volume. Here we investigate the efficacy of salvage SRS for recurrent GBM. METHODS: We retrospectively reviewed 34 patients (41 lesions) treated with salvage SRS for recurrent GBM between 2004-2012. Initial surgical treatments were as follows: gross total resection (58%), subtotal resection (24%), and biopsy (18%). All patients were treated with prior radiotherapy. Recurrent disease was treated with salvage SRS with a median dose of 23.4 Gy (range 12-30) and delivered in a median fraction number of 3 (range 1-3). Cox proportional hazards regression was conducted to establish prognostic factors (p < 0.05). RESULTS: Median follow-up from salvage SRS was 10.8 months (IQR 7.0-15.6). The median time from initial radiotherapy to salvage SRS was 13.7 months (IQR 2.9-25.0). The 6- and 12-month overall survival from salvage SRS were 84.9% and 42.5%, respectively. Upon univariate analysis, subtotal resection (HR = 2.8, p = 0.021) was associated with inferior survival from salvage SRS. The 6- and 12-month local control estimates were 63.1%, and 16.4%, respectively. Using univariate analysis, higher BED (HR = 0.99, p = 0.018) was associated with superior local control. Neither time to recurrence or recurrent tumor volume were associated with local failure. Concerning toxicity, there were 4 (12%) grade 2 and 1 (3%) grade 3 radiation-related toxicities. No grade 4 or 5 toxicities were observed. CONCLUSIONS: Salvage radiosurgery provides an intriguing treatment option for recurrent GBM with minimal toxicity. Our outcomes suggest this is a feasible treatment option with acceptable salvage survival rates given the poor prognosis this diagnosis carries.