Hypofractionation Trial of Re-irradiation in Good Prognosis Recurrent Glioblastoma

* INCLUSION CRITERIA: * Histologic diagnosis of primary glioblastoma or gliosarcoma of the brain, or secondary glioblastoma of the brain due to transformation from a lower grade to a grade 4 tumor. * Age \>= 18. * KPS \>= 70%. * Previous tumor irradiation to curative-intent doses. * Radiation dose constraints must be achievable based on assessment with MRI and treatment planning CT. * Participants must have adequate organ and marrow function as defined below: * Absolute neutrophil count (ANC) \>= 1,000/microL * Platelets \>= 100,000/microL * Individuals of child-bearing potential (IOCBP) and individuals who can father children must agree to use effective contraception (barrier, hormonal, intrauterine device, surgical sterilization, abstinence) from study entry and through 6 months after the last study treatment (restricted period). Individuals who can father children must not freeze or donate sperm within the same period. * Nursing participants must be willing to discontinue nursing from study treatment initiation through 6 months after the last study treatment. * The ability of a participant to understand and the willingness to sign a written informed consent document. EXCLUSION CRITERIA: * Recent systemic therapy prior to the initiation of the study therapy as follows: * Bevacizumab used for reasons other than tumor progression or symptomatic management within 2 weeks. * Temozolomide within 2 weeks. * Cytotoxic chemotherapy within 3 weeks. * Any investigational agents within 2 weeks. * Participants who are unable to undergo MRI evaluation or receive gadolinium contrast for any reason. * Any prior therapy after surgical re-resection or biopsy within 2 weeks prior to the initiation of the study therapy. * Requiring radiation therapy within 12 months prior to the initiation of study therapy. * History of prior therapy with Novacure TTF, Gliadel wafers, or GammaTile therapy. * Positive beta-human chorionic gonadotropin (HCG) pregnancy test performed in individuals of childbearing potential at screening. * Participants with known or suspected radiation sensitivity syndromes. * Uncontrolled intercurrent illness evaluated by medical history and physical exam that are not stable and would potentially increase the risk to the participant.