55. A RANDOMIZED, MULTICENTER PHASE III TRIAL OF SURGERY PLUS STEREOTACTIC RADIOSURGERY (SRS) COMPARED WITH SURGERY PLUS PERMANENTLY IMPLANTED COLLAGEN TILE BRACHYTHERAPY (CTBT) FOR RESECTABLE METASTATIC BRAIN TUMORS-PROTOCOL IN PROGRESS

BACKGROUND: Resection (R) followed by single or multi-fraction stereotactic radiosurgery (SRS) lowers resection bed recurrence compared to R alone. Nevertheless for larger brain metastasis (>2.5 cm) 12-month recurrence rates after R+SRS can exceed 20–30%. Aiming to improve outcomes, a permanently implanted collagen tile brachytherapy (CTBT) device (GammaTile, GT Medical Technologies, Tempe AZ) utilizing Cs-131 was developed, hypothesizing that immediate adjuvant radiotherapy (RT) and/or RT dose intensification could improve outcomes. The device received FDA clearance for this indication, based on a single-arm pre-commercial study and in early commercial use due to the excellent safety and local control of R+CTBT. It is hypothesized that R+CTBT will increase the time to post-resection-recurrence, while prolonging survival and reducing the impact on functional and neurocognitive status compared to R+SRS. STUDY DESIGN: Multicenter, randomized, comparison trial. Patients with resectable, previously untreated “index” brain metastases measuring >2.5–5 cm and 0–3 other tumors will be preoperatively randomized 1:1 to undergo either R+ SRS or R+CTBT to the index lesion; unresected tumors in both groups will receive SRS. Planned sample size is 160 from ~5 sites; accrual to start in Q3-2020. Primary endpoint is surgical bed-recurrence free survival. Secondary endpoints include overall survival, quality of life (Functional Assessment of Cancer Therapy-Brain, Linear Analog Self-Assessment), neurocognition (Hopkins Verbal Learning Test, Trail Making Tests, Mini-Mental Status Exam, Controlled Oral Word Association), functional decline (Karnofsky Performance Scale, Barthel-ADL), and adverse events. Follow-up will be at 1,3,6,9, and 12 months, then q 6 months through 5 years. CONCLUSIONS: This will be the first randomized trial comparing R+SRS versus R+CTBT delivered by Cs-131 sources in permanently implanted resorbable collagen tile carriers. Primary and secondary outcome measures will be captured to elucidate the potential risks and benefits of these two differing approaches for patients with metastatic brain tumors.