Continuous Glucose Monitoring for the Management of Hyperglycemia in Patients With Glioblastoma

Inclusion Criteria: * Presumed newly diagnosed GBM based on imaging findings consistent with GBM on brain MRI (e.g., heterogeneously enhancing mass with central necrosis and surrounding edema), as determined by the treating neuro-oncology team * Age ≥ 18 years at the time of consent * Negative serum pregnancy test within 7 days prior to registration for individuals of childbearing potential * Karnofsky performance status (KPS) ≥ 70 at baseline * Absolute neutrophil count (ANC) ≥ 1.5 × 10\^9/L (performed within 14 days prior to registration) * Platelet count ≥ 100 × 10\^9/L (performed within 14 days prior to registration) * Hemoglobin ≥ 9 g/dL (performed within 14 days prior to registration) * Serum creatinine ≤ 1.5 × upper limit of normal (ULN) or creatinine clearance ≥ 60 mL/min (performed within 14 days prior to registration) * Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤ 2.5 × ULN (performed within 14 days prior to registration) * Total bilirubin ≤ 1.5 × ULN (performed within 14 days prior to registration) * Willingness and ability to comply with CGM device use and attend dietary counseling sessions as per standard of care Exclusion Criteria: * Recurrent glioblastoma * History of eating disorders (e.g., anorexia nervosa, bulimia) or substance use disorder within the past 12 months * Any other uncontrolled or inadequately managed medical illness (e.g., unstable cardiovascular, hepatic, renal, or psychiatric condition) that, in the opinion of the investigator, would interfere with study participation or interpretation of results * Concurrent diagnosis of another active malignancy requiring treatment * Pregnancy or breastfeeding at the time of registration * Documented history of type 1 diabetes mellitus