Minimizing the uncertainties regarding the effects of delaying radiotherapy for Glioblastoma: A systematic review and meta-analysis

Abstract Background and purpose Previous studies have provided no clear conclusions regarding the effects of delaying radiotherapy (RT) in GBM patients. We present a systematic review and meta-analysis to address the effect of delayed RT on the overall survival (OS) of GBM patients. Methods A systematic search retrieved 19 retrospective studies published between 1975 and 2014 reporting on the waiting time (WT) to RT for GBM patients. The meta-analysis was performed by converting WT to RT studies intervals into a regression coefficient ( β ) and standard error expressing the effect size on OS per week of delay. Results Data required to calculate the effect size on OS per week of delay were available for 12 studies (5212 patients). A non-adjusted model and a meta-regression model based on well-recognized prognostic factors were performed. No association between WT to RT, per week of delay, and OS was found (HR=0.98; 95% CI 0.90–1.08; p =0.70). The meta-regression adjusted for prognostic factors weighted by the inverse-variance (1/SE 2 ) showed no clear evidence of the effect of WT to RT, per week of delay, on OS. Conclusions This meta-analysis, despite limitations, provided no evidence of a true effect on OS by delaying RT in GBM patients.