INNV-05. OUTCOMES OF RECURRENT GLIOBLASTOMA PATIENTS WITH RADIATION NECROSIS FOLLOWING GAMMATILE BRACHYTHERAPY IMPLANTATION

Abstract

Abstract Implantation of collagen tile brachytherapy GammaTile (GT Medical Technologies Tempe, AZ) allows for targeting of radiation to residual malignancy following surgical resection of gross disease. Radiation necrosis (RN) can develop after radiotherapy or brachytherapy. We sought to determine outcomes in recurrent glioblastoma patients with RN after treatment with Gammatile. All patients were previously treated with surgical resection followed Stupp protocol chemoradiation. At recurrence, patients underwent repeat surgical resection and implantation of GammaTile. Subsequent MRIs were assessed for stability, presumed RN or progression. Symptomatic RN patients were treated with corticosteroids or bevacizumab. From December 2020 to February 2023, 19 patients were treated. Median time from initial radiation to GammaTile therapy was 270 days. A total of 8 patients (42%) developed RN at a median time of 81 days from GammaTile. In RN patients vs those that did not develop RN, pathological tumor viability was lower (20% vs 50%, p=0.3), age was lower (54 vs 63, p=0.06), tumor volume was lower (10.8 cc vs 51.9 cc, p=0.02), time from initial surgery was longer (470 days vs 299 days, p=0.46), number of GammaTiles placed was lower (5 vs 8, p=0.045), rate of gross total resection (GTR) was higher (100% vs 64%, p=0.04), and MGMT methylation rate was higher (63% vs 11%, p=0.03). No patients in the RN group experienced radiographic progression (0% vs 45%, p=0.009) and 3 (38%) required bevacizumab therapy. Median overall survival from GammaTile surgery in the RN group was 325 days vs 188 days (p=0.03). Our series demonstrates a significant survival benefit in patients who develop RN following GammaTile implantation after glioblastoma recurrence. RN developed in younger patients with smaller tumor volumes, lower pathological tumor viability, and higher rates of GTR and MGMT methylation status.