RADT-09. COMPARATIVE OUTCOMES OF CS-131 BRACHYTHERAPY AND LOW-ENERGY X-RAY INTRAOPERATIVE RADIOTHERAPY FOR BRAIN METASTASES

Abstract PURPOSE Management of brain metastases (BMs) is a balance between achieving optimal disease control while sparing surrounding tissue. Cs-131 brachytherapy and low-energy X-ray intraoperative radiotherapy (LEX-IORT) offer targeted alternatives to external radiotherapy with high local control and lowered risks of complications like radiation necrosis (RN). This study compares the rates of RN, disease control, and periprocedural complications between these two intraoperative modalities of BM management. METHODS We conducted a comparative analysis of aggregated data from two systematic reviews performed by our group on Cs-131 brachytherapy and IORT in BM management. Studies were systematically identified through searches in MEDLINE/PubMed, Embase, Cochrane Library, and ClinicalTrials.gov according to PRISMA guidelines. Data extraction included study design, patient demographics, intervention details, and outcomes. Chi-square testing was used to compare RN rates with an alpha level of 0.05. RESULTS Twenty-two studies were included, analyzing a total of 594 patients of which 329 were treated with IORT and 265 with Cs-131. Median follow-up ranged from 5-19.3 months for Cs-131 patients and 7.2-12.2 for IORT patients. Aggregated RN rates were 17.5% for Cs-131 with GammaTile (GT), 4.9% for IORT, and 1.3% for Cs-131 suture-stranded seeds. A significant difference in the rates of RN was observed between Cs-131 GT and IORT (p = 0.000537) as well as between Cs-131 GT and Cs-131 seeds (p < 0.00001). No significant differences appeared within new or recurrent lesions when stratified by recurrence. Local control rates at 1-year were high for all modalities: Cs-131 GT (79-100%), Cs-131 seeds (83.3-100%), and IORT (84.2-97.1%). Distant control was variable, with Cs-131 seeds at 46.7-52% and IORT at 13-73.5%. Periprocedural complication rates, including bleeding, DVT/PE, and infection, remained low for all modalities (< 4%). CONCLUSION Cs-131 and LEX-IORT provide high local control with low complication rates. Further research is needed to refine treatment protocols for BM.