BIOM-02. A PROSPECTIVE STUDY OF INFLAMMATORY MEDIATORS IN CEREBROSPINAL FLUID AFTER INTRAOPERATIVE RADIOTHERAPY OF BRAIN TUMORS

Abstract BACKGROUND Malignant brain tumors, including gliomas and brain metastases, present therapeutic challenges due to their aggressive nature and high recurrence rates. Intraoperative radiotherapy (IORT) has emerged as promising novel therapy approach that delivers immediate irradiation to the resection cavity. This potentially improves local tumor control and influences the immune response. However, the immunological effects of IORT remain only little understood. METHODS This prospective study included 44 patients undergoing surgical resection of brain tumors, with 20 receiving IORT and 24 serving as controls without IORT. In both groups, cerebrospinal fluid/ wound fluid samples were collected from the resection cavity at multiple predefined intraoperative and postoperative time points. A multiplex proteomic assay was used to measure 19 cytokines involved in inflammation and immune activation. RESULTS IORT led to a significant increases in seven cytokines (IL-1β, IL-6, IL-8, IP-10, MCP-1, MIP-1β, and VEGF) within the IORT group compared to baseline levels. When comparing to the non-IORT group, the increase in IL-1β was significantly greater, while IL-10 least showed a trend towards significance. Subgroup analyses of metastases and gliomas confirmed consistent cytokine increase, with IL-8 showing a significantly greater increase in the metastasis cohort following IORT. CONCLUSION IORT induces distinct changes in cytokine levels, which may contribute to improved tumor control. These findings provide novel insights into the immunomodulatory effects of IORT and may have implications for optimizing multimodal treatment strategies for malignant brain tumors.