SURG-31. DEFINING THE NEW POSSIBILITIES FOR CESIUM BRACHYTHERAPY IN PATIENTS WITH PERIVENTRICULAR GBM

Abstract INTRODUCTION Re-irradiation of patients with external beam radiotherapy (EBRT) for recurrent glioblastoma (GBM) continues to present a therapeutic dilemma due to a high risk of radiation induced necrosis (RN). In contrast, brachytherapy represents a safer, more conformal radiation option aimed at optimizing local control while minimizing the risk of brain tissue damage. Immediate intra-operative implantation with brachytherapy prevents tumor repopulation and offers patients two procedures in one setting. However, due to the risk of seed migration, surgical resection and brachytherapy in periventricular regions was deemed unachievable. In heavily pretreated periventricular GBM, where further EBRT is complicated by RN, a barrier between the ventricular lining and tumor cavity is needed to prevent seed migration. We present two patients where such a barrier allowed successful implantation of brachytherapy to improve disease control. METHODS Two patients, previously treated with surgery and EBRT, presented with recurrent GBM abutting the ventricles. Following GTR of the tumors, a barrier was created by patching the ventricle with Gelfoam to prevent seed migration. Intraoperative brachytherapy implantation of suture stranded Cs-131 seeds (Isoray) for patient 1 and collagen embedded Cs-131 (GammaTile) for patient 2 was performed. A total of 20 Cs-131 seeds on strings threaded through Surgicel, and 6 GammaTiles (24 Cs-131 seeds), were used implanted in patients 1 and 2, respectively. Surgicel covered the implanted seeds and the resection cavity filled with Adherus. RESULTS Post-operative CT scan demonstrated all 20 Cs-131 seeds and 24 Cs-131 seeds in the surgical cavities of patients 1 and 2, respectively, and had serial post operative imaging with MRI scans showing Cs-131 seeds layering surgical cavity, as late as 6 months in total follow up. To date, both patients have had durable local control and no seed migration.