CTNI-46. A RANDOMIZED, CONTROLLED, PHASE 3 TRIAL COMPARING POST-SURGICAL STEREOTACTIC RADIOTHERAPY AGAINST SURGICALLY TARGETED RADIATION THERAPY WITH GAMMATILE IN PATIENTS WITH NEWLY DIAGNOSED BRAIN METASTASES

Abstract BACKGROUND 20-40% of all patients with cancer develop brain metastases. Stereotactic radiotherapy (SRT) has become the preferred standard of care after surgical resection, with improved local control (LC) rates over resection alone. However, even with this paradigm, there is a significant risk of local failure as well as a significant incidence of adverse radiation effect (ARE) with fractionated SRT (FSRT), both of which increase with tumor size. Thus, there is an unmet need for improved adjunctive radiation therapy. Surgically Targeted Radiation Therapy (STaRT) using collagen-tile Cesium-131 brachytherapy (GammaTile®, GT Medical Technologies, Tempe, Arizona, USA) is FDA cleared for the treatment of newly diagnosed malignant brain tumors and may offer an advantage in the rate of LC and/or ARE. OBJECTIVE The primary objective is to compare surgical bed recurrence free survival (SBRFS) after surgical tumor removal plus SRT, versus surgical tumor removal plus STaRT. Key secondary objectives include assessments of overall survival, occurrence of leptomeningeal tumors (classical and nodular), quality of life, neurocognitive function, and radiation necrosis, among others. METHODS Prospective, randomized, parallel, open-label, multi-site 230 patient study with 2 study arms: Patients with 1 tumor for resection + SRT to resection bed versus patients with resection of 1 tumor + STaRT to resection bed. Randomization is 1:1 done preoperatively, ≤7 cm preoperative maximum dimension, and 5 additional unresected metastases are allowed, with patients in both arms receiving FSRT/ radiosurgery to any unresected, previously untreated metastases. An interim analysis is planned for August 2025, pending central review.