Beginning Radiation Immediately With GammaTile at GBM Excision Versus Standard of Care

This is a Phase 3 prospective, randomized, superiority, open-label, multi-site study. The overview of this study is as follows: * A Screening/Baseline Period of 21 days. During this time, patients will be randomized into a 1:2 allocation of Arm A:Arm B. * A Perioperative/Operative Phase where patients will undergo tumor resection (Arm A) or tumor resection plus GammaTile implantation (Arm B). * An EBRT Prior to Start Period. This occurs within 10 business days prior to EBRT and Concurrent TMZ Phase. * An EBRT and Concurrent TMZ Phase, which will begin 30 ±10 days post-surgery. EBRT (30 fractions) and TMZ will be administered up to 5 days a week for 6 weeks in Arm A, and EBRT (20 fractions) and TMZ will be administered for up to 5 days a week for 4 weeks in Arm B. TMZ will be administered at a dose of 75 mg/m2/day orally for each Arm. * An Adjuvant TMZ Phase, which begins 28 ±7 days foll