Could a diabetes drug shield your brain after radiation?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Age ≥ 18 years * Diagnosis of brain tumor requiring cranial radiation treatment NOTE: Patient may be enrolled during or up to 5 years after completion of cranial radiation administered for treatment of primary or metastatic intracranial tumor * Eastern Cooperative Oncology Group (ECOG) performance status of 0, 1, or 2, AND Karnofsky performance status (KPS) of ≥ 70 * Expected survival ≥ 6 months in the opinion of treatment team * Willing and able to adhere with the protocol for the duration of the study including undergoing treatment, and attending scheduled visits, and examinations * The following laboratory values obtained ≤ 30 days prior to registration: * Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤ 3 x ULN \[≤ 5 x upper limit normal (ULN) for patients with baseline liver disease\] * Negative pregnancy test ≤ 8 days prior to registration for persons of childbearing potential only * Ability to complete cognitive assessments and questionnaires by themselves or with assistance Exclusion Criteria: * Uncontrolled and/or intercurrent illness or other condition which limits safety of or compliance with study proceedings * Pregnant or nursing, imprisoned, or lacking capacity for understanding * Unable to swallow tablets or at risk for impaired absorption of oral medication * Currently taking the study agent (i.e., metformin), and cannot safely discontinue if randomized to the control group (Group B) * Known hypersensitivity or allergy to metformin * Current use of resveratrol, CoQ10 (coenzyme Q10), coconut oil/other medium chain triglyceride-containing (e.g., Axona) supplements, or curcumin and unwilling to discontinue prior to registration and remain off these agents for study duration * Unable to read and speak English. Note: English doses not to need to be primary language