EFFECTIVENESS OF BEVACIZUMAB TO MANAGE SYMPTOMATIC STEROID REFRACTORY PSEUDOPROGRESSION OCCURRING DURING OR EARLY FOLLOWING RADIATION THERAPY FOR GLIOBLASTOMA

Abstract AIMS Approximately 15% of patients with glioblastoma (GBM) managed with Stupp Protocol(Stupp60Gy), experience symptomatic steroid-refractory mass effects from pseudoprogression resulting in significant morbidity. Beva- cizumab (BEV) potentially produces a clinical response allowing corticosteroid minimisation and completion of definitive therapy. This study examines the clinical and radiological volumetric outcomes following early BEV (earlyBEV), defined as commencement during or within 3 months of IMRT completion. METHODS Consecutive patients managed with earlyBEV for Glioblastoma(IDHwt) with Stupp60Gy between 2016-2023 were identified from a prospective database. The preBEV and postBEV (month+2/3) scans were used for vol- umetric response. Calculation of midline shift at 3rd/lateral ventricle was performed. Baseline patient/tumour characteristics were assessed. Pattern of relapse, specifically distant failure outside of initial GTV was assessed. The primary endpoint was volumetric reduction of T1gd/T2 volumes at month+2/3 post BEV. Secondary endpoints were survival outcomes compared with overall cohort. RESULTS 284 patients were managed, of which forty (14%) received early BEV. Compared to remaining 244 patient cohort, earlyBEV had worse initial ECOG0,1 (50%vs76%); less near-total resection (5%vs42%) and less MGMT methyla- tion (35%vs46%). Median time to earlyBEV was 1.4months postIMRT, including seven patients before IMRT completion. Median T1gd/T2 volumes before earlyBEV were 36cm3(q1-3:22-62cm3) and 114cm3(q1-3:89-147cm3). All patients re- sponded to BEV, though one patient had stable T1gd, and one died before reassessment. The median volumes postBEV were 16cm3(q1-3:7-23cm3) and 40cm3(28-53cm3); with median volume reduction of 65% and 67%. The overall survival (mOS) post BEV commencement was 8.1months (95%CI:7.5-8.6). The mOS post diagnosis was 11.9months (95%CI:8.9-14.0) vs 19.9months (95%CI:18.1-21.6) for the whole cohort (p<0.001). A component of distant relapse was evident in 40% of earlyBEV vs 34% in total cohort. Only one serious adverse event occurred with fatal intracranial haemorrhage at day10 after initial BEV dose. CONCLUSION This study data demonstrates efficacy of earlyBEV for steroid-refractory pseudoprogression, but also confirms the poor prognosis of this high-risk cohort.