Efficacy of bevacizumab therapy for unresectable malignant glioma: A retrospective analysis

Bevacizumab (BEV), an inhibitor of vascular endothelial growth factor A, has been used for primary and recurrent malignant gliomas in Japan since June, 2013. Previous randomized controlled studies demonstrated that BEV prolonged the progression-free survival, but not the overall survival (OS) of patients with newly diagnosed glioblastoma. The aim of the present study was to elucidate the effect of BEV on the OS of patients with unresectable malignant gliomas. Of the 440 cases of malignant glioma initially treated in our institute between 2000 and 2015, 88 were not suitable for maximal resection due to patient age, physical condition, tumor location and extent, or the patient's wishes. Based on the biopsy results, the pathological diagnosis was glioblastoma, anaplastic astrocytoma and anaplastic oligodendroglioma in 60, 19 and 9 patients, respectively. Kaplan-Meier and log-rank analyses were performed to investigate the effect of BEV on OS. OS was longer in the BEV group (n=24) compared with that in the non-BEV group [n=64; median survival time (MST), 566 vs. 243 days, respectively; hazard ratio (HR)=0.413; 95% confidence interval (CI): 0.216-0.787; P=0.003]. In the 41 patients who received temozolomide (TMZ) and radiotherapy and the 31 patients with glioblastoma who received TMZ and radiotherapy, OS was longer in the BEV group compared with that in the non-BEV group (MST, 568 vs. 334 days, HR=0.404, 95% CI: 0.175-0.933, P=0.016; and MST, 566 vs. 160 days, HR=0.253, 95% CI: 0.099-0.646, P=0.001, respectively). In the Cox hazard model analysis of 41 patients who underwent TMZ-based chemoradiotherapy after biopsy, the use of BEV was the strongest independent beneficial factor associated with prolonged OS (HR=0.101; P=0.0002). Our retrospective survey suggested that BEV prolongs the OS of patients with unresectable malignant gliomas. However, these results must be verified by a well-designed prospective randomized controlled trial.