SURG-44. TO PROCEED OR NOT TO PROCEED: THE IMPACT OF FROZEN SECTION PATHOLOGY ON INTRAOPERATIVE BRAIN BRACHYTHERAPY IMPLANTATION FOR RECURRENT GLIOBLASTOMA

Abstract BACKGROUND Glioblastoma (GBM) is a highly aggressive malignancy that recurs in up to 90% of patients following standard-of-care therapy, including surgical resection, concurrent chemoradiotherapy, and subsequent adjuvant chemotherapy. In cases of prior radiation therapy (RT) use, one option for localized, recurrent GBM (RGBM) is STaRT (Surgically Targeted Radiation Therapy) (GammaTile, GT Medical Technologies, Tempe AZ USA), a form of brachytherapy utilizing cesium-131 seeds implanted at the time of re-resection. One of the potential concerns with STaRT implantation for RGBM is that intraoperative frozen section pathology may demonstrate only necrosis, in which case further RT may not be advisable. This concern is often cited as a deterrent to offering an intraoperative brachytherapy treatment in RGBM cases. Herein we review the frequency of intraoperative frozen section diagnosis returning radiation necrosis leading to aborted GammaTile placement. METHODS The GammaTile Registry, a prospectively enrolling multi-center phase 4 study (NCT04427384), was assessed for all patients receiving intraoperative brachytherapy for RGBM from 10/2020 to 3/2024. Data regarding patient demographics, procedure details, and pathology were extracted and analyzed. RESULTS A total of 122 RGBM patients with a median age of 59 years (range 28-86) were scheduled for STaRT. Of these, 109 (89.3%) patients had confirmed prior radiation with a median RT dose of 60.0Gy (range 16-75). Only two (1.6%) planned cases of GammaTile placement were aborted after intraoperative frozen section pathology demonstrated extensive radiation necrosis without viable tumor. The patients had received fractionated RT to 55.8Gy and 60.0Gy, respectively. While both frozen samples were predominantly necrosis, the final pathology demonstrated foci of residual glioblastoma in both cases. CONCLUSIONS While it is uncommon in RGBM to abort STaRT due to intraoperative pathology indicating only radiation necrosis, careful consideration should be given when aborting the procedure as in this series final pathology ultimately demonstrated viable tumor cells.