Bevacizumab in recurrent glioblastoma: open issues

Recurrent glioblastoma represents a challenge in neuro-oncology since the prognosis is poor and current therapeutic options are limited. Bevacizumab has demonstrated activity in this setting in various clinical trials and has been approved by US FDA for the treatment of recurrent glioblastoma. Nevertheless, many issues still exist. In this article, we summarized the principal subjects of controversies that surround bevacizumab and its use in the treatment of recurrent glioblastoma.

Primary and secondary gliosarcomas: clinical, molecular and survival characteristics

Gliosarcoma is classified by the World Health Organization as a variant of glioblastoma. These tumors exhibit biphasic histologic and immunophenotypic features, reflecting both glial and mesenchymal differentiation. Gliosarcomas can be further classified into primary (de novo) tumors, and secondary gliosarcomas, which are diagnosed at recurrence after a diagnosis of glioblastoma. Using a retrospective review, patients seen at MD Anderson Cancer Center between 2004 and 2014 with a pathology-confirmed diagnosis of gliosarcoma were identified. 34 patients with a diagnosis of gliosarcoma seen at the time of initial diagnosis or at recurrence were identified (24 primary gliosarcomas (PGS), 10 secondary gliosarcomas (SGS)). Molecular analysis performed on fourteen patients revealed a high incidence of TP53 mutations and, rarely, EGFR and IDH mutations. Median overall survival (OS) for all patients was 17.5 months from the diagnosis of gliosarcoma, with a progression free survival (PFS) of 6.4 months. Comparing PGS with SGS, the median OS was 24.7 and 8.95 months, respectively (from the time of sarcomatous transformation in the case of SGS). The median OS in SGS patients from the initial diagnosis of GB was 25 months, with a PFS of 10.7 months. Molecular analysis revealed a higher than expected rate of TP53 mutations in GS patients and, typical of primary glioblastoma, IDH mutations were uncommon. Though our data shows improved outcomes for both PGS and SGS when compared to the literature, this is most likely a reflection of selection bias of patients treated on clinical trials at a quaternary center.

Novel chemotherapeutics and other therapies for treating high-grade glioma

INTRODUCTION

Despite extensive research, high-grade glioma (HGG) remains a dire diagnosis with no change in the standard of care in almost a decade. However, recent advancements uncovering molecular biomarkers of brain tumors and tumor-specific antigens targeted by immunotherapies provide opportunities for novel personalized treatment regimens to improve survival.

AREAS COVERED

In this review, the authors provide a comprehensive overview of recent therapeutic advancements in HGG. Furthermore, they describe new molecular biomarkers and molecular classifications, in addition to updated research on bevacizumab, targeted molecular therapies, immunotherapy and alternative delivery methods that overcome the blood-brain barrier to reach the target tumor tissue. Challenges regarding each therapy are also outlined. The authors also provide some insight into a novel non-chemotherapeutic treatment for malignant glioma, NovoTTFA, as well as a summary of current treatment options for recurrence.

EXPERT OPINION

Current research for treating malignant gliomas are paving the path to personalized therapy, including immunotherapy, that involve integrated genomic and histolopathologic data, as well as a multi-modal treatment regimen. Immunotherapy will potentially be the next addition to the current standard of care, specialized to the antigens presented on the tumors. The results of the current trials of multi-antigen vaccines are eagerly anticipated.