10002-CS-1 Validation of clinical prognosis in patients with newly diagnosed glioblastoma treated by preoperative neoadjuvant bevacizumab therapy

Abstract Purpose The validation was conducted to explore prognostication of preoperative neoadjuvant bevacizumab (neoBev) for newly diagnosed glioblastoma. Methods We retrospectively reviewed 33 patients. Patients were enrolled based on typical magnetic resonance imaging (MRI) suggestive of GB. Surgery was performed between days 21 and 30 (mean; 24.2 days) after neoBev. The efficacy of neoBev were evaluated by mean overall survival (mOS) compared with standard therapy after propensity score matching as control. In the neoBev, prognostication was validated by extent of resection (EOR) and response rate on T1-weighted imaging with gadolinium-enhancement (T1Gd) and fluid-attenuated inversion recovery (FLAIR). EOR was defined by RANO2. 0 criteria as gross total resection (GTR;with no residual tumors), subtotal resection (STR;EOR more than 90%). Results Final diagnosis was glioblastoma, IDH-wildtype in 31 cases and GB and IDH-mutant in 2 cases. median KPS of before and after neoBev were 71.2 and 83.0, respectively, which was significantly different from control (69.7 and 69.3, respectively). The volume reduction rate after neoBev was stratified as good responder (GR) and poor responder (PR) by 37% and 55% cutoff for T1Gd and FLAIR, respectively. In FLAIR, mOS in GR and PR were 13.4 months and 14.1 months, respectively (P = 0.49). In T1Gd, mOS in GR and PR were 17.3 months and 9.7 months, respectively (P < 0.01), which was statistically significant. Regarding to EOR, in the GTR group, mOS in neoBev and control were 18.0 months and 23.2 months, respectively (p = 0.36). Whereas, in the STR group, mOS in neoBev and control were 18.8 months and 13.2 months, respectively (p = 0.72). Conclusion Although mOS were prolonged in GR on T1Gd, preoperative neoBev did not contribute to prolong OS compared with control, probably due to under-estimation of GTR and microscopic infiltration. Given that initial GR of neoBev, appropriate selection might provide clinical benefit for patients with newly diagnosed GB.