In addition, our subgroup analysis also revealed that KPS was a significant prognostic factor whereas age and MGMT status both appeared to demonstrate some effect but were not statistically significantly different, findings that have been replicated in many other clinical trials in GBM.23–25 We acknowledge that the use of historical controls to assess efficacy in clinical trials is a limitation of our study based on literature in the field highlighting the changes in overall hazard profile between contemporary and historical patients.26 The gene discussed is MGMT; the disease is glioblastoma.