Question: Can valproic acid prolong survival of glioblastoma patients?

Context:
For patients who presented with epilepsy, the use of the antiepileptic drug VPA did not associate with survival when compared with patients who did not receive VPA treatment.
This prognostic effect is not solely explained by early diagnosis, and survival is not associated with VPA treatment.
Several in vivo and in vitro studies have indicated that VPA has radiosensitizing effects for gliomas and radioprotective influence on normal brain tissue or hippocampal neurons. The results of several retrospective studies have also indicated potential benefit to improve survival of patients with GBM. Moreover, the promising treatment results of a phase 2 trial of concurrent radiation therapy, temozolomide, and VPA for patients with GBM have been recently reported. 
While there have not been any novel anti-GBM therapeutics approved for many years, there has been the gradual accumulation of clinical data suggesting that the widely used anti-convulsant agent, valproic acid (VPA) may significantly prolong survival in GBM patients.
 Additionally, VPA may result in improved outcomes compared to historical data and merits further study.
Several retrospective studies in seizure patients with glioblastoma treated with chemotherapy have provided evidence for a moderately improved survival with the use of valproic acid, possibly due to inhibition of histone deacetylase
Several clinical studies have reported that valproic acid could prolong survival of GBM patients
While there have not been any novel anti-GBM therapeutics approved for many years, there has been the gradual accumulation of clinical data suggesting that the widely used anti-convulsant agent, valproic acid (VPA) may significantly prolong survival in GBM patients
Prolonged survival with valproic acid use in the EORTC/NCIC temozolomide trial for glioblastoma
Prolonged survival with valproic acid use in the EORTC/NCIC temozolomide trial for glioblastoma.
Valproic acid use during radiation therapy for glioblastoma associated with improved survival.
Patients receiving VPA alone (97 [16.9%]) appeared to derive more survival benefit from TMZ/RT (hazard ratio [HR] 0.39, 95% confidence interval [CI] 0.24-0.63) than patients receiving an EIAED only (252 [44%]) (HR 0.69, 95% CI 0.53-0.90) or patients not receiving any AED (HR 0.67, 95% CI 0.49-0.93). 
Several retrospective studies in seizure patients with glioblastoma treated with chemotherapy have provided evidence for a moderately improved survival with the use of valproic acid, possibly due to inhibition of histone deacetylase.
Several uncontrolled retrospective case series and a post hoc analysis of the registration trial for temozolomide indicated an association between valproic acid (VPA) use and improved survival outcomes in patients with newly diagnosed glioblastoma.To confirm the hypothesis suggested above, a combined analysis of survival association of antiepileptic drug use at the start of chemoradiotherapy with temozolomide was performed in the pooled patient cohort (n = 1,869) of four contemporary randomized clinical trials in newly diagnosed glioblastoma: AVAGlio (Avastin in Glioblastoma; NCT00943826), CENTRIC (Cilengitide, Temozolomide, and Radiation T
Several clinical studies have reported that valproic acid could prolong survival of GBM patients.
Patients receiving VPA alone (97 [16.9%]) appeared to derive more survival benefit from TMZ/RT (hazard ratio [HR] 0.39, 95% confidence interval [CI] 0.24-0.63) than patients receiving an EIAED only (252 [44%]) (HR 0.69, 95% CI 0.53-0.90) or patients not receiving any AED (HR 0.67, 95% CI 0.49-0.93).VPA may be preferred over an EIAED in patients with glioblastoma who require an AED during TMZ-based chemoradiotherapy.
The combination of radiotherapy, temozolomide and valproic acid (VPA) has shown some promise in retrospective analyses of patients with glioblastoma, although their mechanisms of action remain unknown.We investigated the in vitro and in vivo effects of pretreating glioma cells with temozolomide and VPA as an immunization strategy to boost an adaptive immune response in a syngeneic mouse model.Temozolomide and VPA induced autophagy in GL261 glioma cells, and caused tumor antigen-specific T-cells to become activated effector T-cells.
Prolonged survival with valproic acid use in the EORTC/NCIC temozolomide trial for glioblastoma.

Answer: Yes, there is evidence to suggest that valproic acid (VPA) is associated with prolonged survival of glioblastoma patients. Several studies have indicated that VPA has radiosensitizing effects for gliomas and radioprotective influence on normal brain tissue or hippocampal neurons.
Exact answer: yes