G-CSF After Chemo-radiation in Patients With Glioblastoma

Inclusion Criteria: * Participants must have confirmed newly diagnosed glioblastoma multiforme (GBM), World Health Organization (WHO) grade 4, IDH wildtype, either by histological or molecular criteria. * Molecular analysis needs to confirm a positive MGMT promoter methylation status using standard institutional testing methods. * Treatment needs to involve a planned 6-week course of standard of care radiation therapy with concurrent and adjuvant 6 monthly chemotherapy with temozolomide. Patients scheduled to receive an abbreviated radiation course (e.g., 3 weeks in elderly patients) are eligible. * Age ≥18 years. GBM is considered a biologically distinct disease in children. Children are excluded from this study but will be eligible for future pediatric clinical trials. * Karnofsky Performance Status (KPS) \> 60, see Appendix A * No prior cranial irradiation. * No existing diagnosis of clinical dementia or high clinical suspicion for presence of any neurodegenerative disease (e.g., Alzheimer's Disease, Fronto-temporal Dementia (FTD), Parkinson's Disease, Motor Neuron Disease, etc.) prior to diagnosis of GBM. * Life expectancy of greater than 6 months. * Must be able to undergo repeated brain Magnetic resonance imaging (MRI) studies with administration of gadolinium (contrast enhanced brain MRI). * Participants must have adequate organ and bone marrow function (as defined below) to be able to receive standard chemoradiation therapy: * leukocytes ≥2,500/mcL * absolute ne…