- Residual disease of recurrent glioblastoma is not mandated for eligibility into the study. To best assess the extent of residual disease post-operatively, a post-operative MRI scan must be performed prior to registration and is recommended to be within 96 hours post-surgery (although 24-48 hours would be optimum). Note: Patients who did have surgery with a post-operative contrast-enhanced scan falling outside the 5-week window prior to registration, must have a repeat MRI scan within 14 days prior to registration.