BIOM-39. GENOMIC AND CLINICAL ASSOCIATIONS WITH RADIATION NECROSIS IN PATIENTS WITH DIFFUSE INFILTRATING GLIOMAS

Abstract BACKGROUND Radiation necrosis (RN) is a complication of radiotherapy (RT) that can significantly affect quality of life and outcomes in patients with gliomas. Clinical and molecular factors predisposing patients to RN are not clearly established. We hypothesize that clinicogenomic data can be leveraged to identify patients at high risk for RN. METHODS We identified patients from 2014-2024 with diffuse gliomas and RN diagnosed based on Advanced-Brain-Tumor-Imaging which includes conventional MRI, 3 perfusion parameters, spectroscopy and/or pathology at MD Anderson. Inclusion criteria included diagnosis of RN 12-weeks after RT and concordance of 4 ABTI parameters. For each case, we identified 2 controls who were gender-,diagnosis-, and age-matched using a nearest neighborhood algorithm. We evaluated the correlation between 15 most mutated genes in baseline tissue and occurance of RN. A logistic regression model was employed to assess the multivariable relationship between patient characteristics, gene mutations, and RN. RESULTS We identified 62 patients with RN; 50 glioblastoma (80.6%), 8 diffuse astrocytoma (12.9%) and 4 oligodendroglioma (6.5%). Time from RT to RN diagnosis was 254 days (IQR 154-483). 18(29%) of RN cases and 29(24.4%) of controls had received more than one course of RT. Patients treated with bevacizumab before RT had significantly lower odds of developing RN compared to those who did not receive bevacizumab (OR 0.103 [0.011 – 0.960], p=0.0459). BRAF mutations were more frequent in the RN cohort (8.1% vs. 2.4%) and patients with BRAF mutation were more likely to have RN than those without BRAF mutation (OR 6.842 [1.2, 39.01], p=0.0304). Age, gender, diagnosis, IDH, MGMT or 1p19q status were not associated with RN. CONCLUSION We found that bevacizumab administration was associated with a significant reduction in RN development. We also found a novel association between presence of BRAF mutations and increased risk of RN in glioma patients, which warrants further investigation.