CTNI-19. RESECTION AND CESIUM-131 RADIATION SOURCES IMBEDDED IN BIO-RESORBABLE COLLAGEN TILES (GAMMATILE™) FOLLOWED BY THE STUPP PROTOCOL IN NEWLY-DIAGNOSED GLIOBLASTOMA: GESTALT TRIAL-IN-PROGRESS UPDATE

Abstract

Abstract OBJECTIVE To evaluate the safety and feasibility of combining resection with immediate initiation of radiation and subsequent Stupp protocol in newly-diagnosed glioblastoma (GBM). BACKGROUND Rapid early local progression (REP) after resection, prior to the initiation of EBRT+/-chemotherapy, occurs in 25-50%. This high-rate of REP supports initiation of an effective postoperative treatment as early as safely possible. Bio-resorbable collagen tiles with imbedded cesium-131 radiation sources (Gammatiles™) are FDA cleared for this use. Intraoperatively, tiles are placed within the resection bed, thus achieving an immediate initiation of surgically targeted radiation therapy (STaRT). DESIGN/ METHODS GESTALT is a single-arm 61 patient multi-center trial. Consented adults with suspected or confirmed GBM undergo a maximum safe resection with Gammatile™ (STaRT). Patients with molecular GBM (WHO 2021 criteria) start concurrent EBRT/Temozolomide beginning 25±4 days post-surgery. Subsequent EBRT (20 fractions, 4 weeks) to low and high-risk PTV takes Gammatile™ dose into account to a combined biologically equivalent dose of 46 and 60 Gy delivered in 2Gy/fraction, respectively. Adjuvant TMZ (6 cycles) begins 28±7 days after EBRT/Temozolomide. TTF is allowed. IDH-mutated gliomas are followed for safety. Outcomes include feasibility of incorporating Gammatile™ without delay of Stupp protocol, consent/attrition rates, safety, performance status trajectory (ECOG, KPS), immune competence (absolute lymphocyte counts), local control, PFS, and OS. RESULTS The trial opened in Fall 2022 at 4 sites. 12 additional sites are onboarding (NCT05342883). 16 patients are on trial as of abstract submission. Currently, this trial appears feasible and without any unexpected intolerances/toxicities. CONCLUSIONS This is the first trial in newly diagnosed GBM patients to combine resection, Gammatile™, and the Stupp protocol, in an attempt to reduce REP, as well as possibly, improve other outcomes. RESULTS will inform the routine and investigational use of Gammatile™, and if suggestive, will form the basis for a subsequent randomized trial.