NIMG-58. PET IMAGING AS A RELIABLE INDICATOR FOR EVALUATING BEVACIZUMAB TREATMENT RESPONSE IN GBM

Abstract OBJECTIVE PET scans are crucial for glioma diagnosis and treatment planning, but assessing the efficacy of Bevacizumab (Bev) treatment using MRI alone is challenging. Our study aimed to evaluate the effectiveness of Bev-based glioblastoma treatment using PET scans. METHODS We included ninety glioblastoma patients treated with Bev between July 2013 and May 2023. Patients were divided into three groups: the first group received Bev in addition to the Stupp regimen after biopsy or subtotal resection (first-dose group), the second group received Bev after biopsy followed by tumor resection (neoadjuvant group), and the third group received the Stupp regimen followed by TMZ + Bev at recurrence (recurrent group). PET scans (FDG, MET, FLT, and FMISO) were performed before and 4 weeks after starting Bev treatment. Tumor-to-normal ratio (TNR) was calculated for FDG, MET, and FLT, and tumor-to-blood ratio (TBR) was determined for FMISO. We used the Cox proportional hazards model to assess the percent change in TNR, TBR, and metabolic tumor volume (MTV) as prognostic factors. RESULTS The median PFS and OS (month) from Bev treatment were as follows: first-dose group (PFS: 8.87, OS: 12.53), neoadjuvant group (PFS: 16.53, OS: 22.13), and recurrent group (PFS: 4.0, OS: 8.0). In the first-line group, significant differences were found in the percent change in MTV for MET, FLT, and FMISO. In the recurrent group, significant differences were observed in the percent change in MTV for FDG and MET, as well as in FDG TNR and FMISO TBR. In the neoadjuvant group, significant differences were found in the percent change in MTV for MET and FLT. CONCLUSION Neoadjuvant Bev treatment led to prolonged PFS and OS in glioblastoma patients. Decreases in MET MTV change rate and FMISO TBR change rate were identified as potential indicators for assessing Bev treatment efficacy after recurrence.