NCMP-14. RADIOGRAPHIC RESPONSE TO BEVACIZUMAB IN TREATING RADIATION NECROSIS AND ASSOCIATED EDEMA IN BRAIN TUMORS

Abstract OBJECTIVE This study evaluates the efficacy of bevacizumab in treating radiation necrosis (RN) and associated perilesional edema in brain tumors. We aimed to measure changes in radiologic volumes and clinical performance following treatment. MATERIALS AND METHODS We retrospectively reviewed patients treated with radiation therapy and/or stereotactic radiosurgery between September 2017 and August 2023. We identified 10 metastatic brain tumors and one glioblastoma with symptomatic RN. Diagnosis was primarily through MRI, with one case confirmed pathologically. All patients received bevacizumab (7.5 mg/kg every 3 weeks). Volumes of RN and perilesional edema were measured using gadolinium-enhanced T1-weighted and T2-weighted/FLAIR MRI, respectively, analyzed with Brainlab software. Volume changes and clinical symptoms, graded by the ECOG Performance Status (PS) scale, were recorded. RESULTS The minimal follow-up was 4 months. The 11 patients received a median of 2 bevacizumab cycles (range, 2-3). Pre-treatment median volumes (ranges) were: tumor/RN 5.45 cc (2.66-13.56), perilesional edema (T2, FLAIR) 53.93 cc (7.46-115.32), 58.01 cc (15.18-131.2). Post-treatment median volumes (ranges) were: tumor/RN 2.5 cc (2.23-7.23), perilesional edema (T2, FLAIR) 4.05 cc (3.08-11.18), 7.38 cc (2.887-17.647). Median percentage volume reductions were: tumor 39%, RN 38%, perilesional edema (T2, FLAIR) 80%, 79%. Significant reductions in edematous volumes were observed. Pre-treatment ECOG PS median was 2 (range 2-3); post-treatment ECOG PS median remained 2 (range 2-3). Clinical performance improved in most patients, with two exception where deterioration occurred after the third cycle despite initial improvement. CONCLUSION Bevacizumab is effective in reducing RN and perilesional edema, particularly within the first two cycles of treatment. Most patients showed clinical improvement, though further research is needed to optimize treatment and understand long-term outcomes.