THERApeutic Outcomes Related to Gut microBIOME in Glioblastoma (GBM) Patients Receiving Chemo-radiation (THERABIOME-GBM)

Inclusion Criteria: * Patients with newly diagnosed WHO grade 4 glioblastoma, IDH-1 R132H wild type * Maximum safe resection (≥70% of initial tumor volume resected) * Age ≥ 18 * Eastern Cooperative Oncology Group (ECOG) performance status 0 to 1 or ECOG 2 if on ≤ 8 mg/day of dexamethasone (or bioequivalent) * Plan to receive 60 Gy / 30 fractions of radiation with temozolomide within 12 weeks of surgery * Patient or substitute decision maker able to provide written informed consent Exclusion Criteria: * Metastatic cancer or secondary cancer that could affect interpretation of primary and secondary study outcomes * Receiving additional systemic therapy / clinical intervention for glioblastoma that would prevent a uniform treatment cohort with temozolomide and radiation x 6 weeks followed by adjuvant temozolomide 150-200 mg/m2 on days 1-5 every 28 days for up to 6 cycles.\* * Inability to collect study stool samples * Any diagnosis or medical condition, physical and / or psychological, that the investigator feels precludes the patient from participation in the study. * If there is a new standard of care treatment for newly diagnosed GBM before the first patient is enrolled (e.g., Optune Tumor Treating Fields), then we will allow all patients on this study to adopt the new standard of care therapy. To allow for maximum patient accrual, if patient chooses to enroll on an open label randomized therapeutic study whereby the control arm involves only the standard of care treatment, then patients enrolled in the control arm could be eligible for this study at the discretion of the investigator.