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 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
• * Coagulation: Prothrombin time (PT) / Partial thromboplastin time (PTT) within institutional normal range.
• * Total and direct bilirubin \< 2 x institutional upper limit of normal (ULN)
• * Aspartate aminotransferase (AST) \< 2 x institutional ULN
• * Alanine transaminase (ALT) \< 2 x institutional ULN
• * Serum creatinine \< 1.5 mg/dL
• * Serum albumin \>= 0.75 x institutional normal range
• * Women of child-bearing potential (WOCBP) and men 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). Men must not freeze or donate sperm within the same period.
• * Breastfeeding participants must be willing to discontinue breastfeeding 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.
• * History of prior therapy with Novacure TTF, Gliadel wafers, or GammaTile therapy.
• * Positive beta-human chorionic gonadotropin (HCG) pregnancy test performed in females 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.