REMIND Maintenance Radiotherapy for Newly Diagnosed Glioblastoma

Inclusion Criteria: * Histologically confirmed diagnosis of glioblastoma according to WHO classification criteria for which standard-of-care surgical resection, concurrent temozolomide and radiotherapy, and adjuvant temozolomide is planned * Planning to receive standard-of-care radiotherapy with a biological effective dose of 60 Gy or less in 30 fractions * Age 18 years or older at the time of consent * Karnofsky performance status of 70 or higher * Life expectancy of 3 months or longer * Adequate organ function confirmed by laboratory values obtained within 14 days of study enrollment, defined as absolute neutrophil count at least 1.5 × 10\^9/L, platelets at least 50 × 10\^9/L, and hemoglobin at least 8 g/dL independent of transfusion within 14 days of screening * Persons of childbearing potential or with partners of childbearing potential must be willing to use contraception during study treatment * Concurrent use of other investigative treatment is permitted * Voluntary written consent prior to the performance of any research-related activity Exclusion Criteria: * Pregnant or breastfeeding * Presence of brain stem involvement within the planning target volume from the initial course of standard-of-care radiotherapy * Prior radiation therapy to the brain * Contraindication to MRI or CT * Uncontrolled intercurrent illness, including ongoing or active infection, hypertension, serious cardiac arrhythmia requiring medication, acute cardiovascular disease or clinically manifested myocardial insufficiency, or psychiatric illness or social situations that would limit compliance with study requirements * Any medical condition or clinical laboratory abnormality that, in the investigator's judgment, precludes safe participation in and completion of the study or could affect compliance with protocol conduct or interpretation of results