GammaTile Cs-131 Brachytherapy + Stupp Cuts Rapid Early Progression to 6% in GBM

GammaTile is a cesium-131 collagen-tile brachytherapy platform implanted at resection to deliver immediate local radiation, then followed by abbreviated EBRT with concurrent/adjuvant temozolomide in the prospective GESTALT feasibility/safety study for newly diagnosed GBM across 15 US centers (mITT n=67; NCT05342883). Feasibility was met, with 74% starting EBRT+TMZ within 21–35 days post-op (median 29 days), and centrally reviewed rapid early progression was 6%, far below literature suggesting rapid early progression can occur in a large fraction of patients during the postoperative gap. Grade ≥3 TRAEs occurred in 39% (22% surgery-only, 18% radiation-only, 13% surgery+radiation), comparable to the ~38% cited for SOC in NRG BN007; median OS was 16.5 months in MGMT-unmethylated disease and 28.0 months in methylated disease, with median PFS 9.3 months and not reached, respectively.