This clinical trial studies the side effects of temporally-modulated pulsed radiation therapy (TMPRT) in patients with IDH-mutant gliomas who have previously received radiation therapy to the brain. TMPRT is a radiation technique in which radiation is delivered in multiple small doses on a specific timed interval, instead of delivering one large dose at one time. This technique may improve efficacy while reducing toxicity and improving patient quality of life.

Inclusion Criteria:

• Histologically confirmed recurrent IDH-mutant gliomas (either astrocytoma or oligodendroglioma) with prior external beam radiation therapy (EBRT) to the same region. The recurrent tumor may be either histologically confirmed or based on clinical assessment. Any number of prior recurrences is allowed.
• Maxium tumor diameter of 7 cm or less.
• Prior EBRT is ≥ 2 years ago.
• The region for reirradiation should have received at least 45 Gy from the prior EBRT but no more than 75 Gy. The prior EBRT could be either photon-based or proton-based.
• Prior SRS to the same region is permitted as long as the cumulative dose of EBRT plus SRS is no more than 75 Gy. The prior SRS should be completed at least 6 months ago.
• Life expectancy ≥ 12 months
• At least 18 years of age.
• Karnofsky performance status (KPS) of at least 70%.
• Females of childbearing potential (defined as a female who is non-menopausal or surgically sterilized) must be willing to use an acceptable method of birth control (i.e., hormonal contraceptive, intra-uterine device, diaphragm with spermicide, condom with spermicide, or abstinence) for the duration of the study. Should a woman become pregnant or suspect she is pregnant while participating in this study, she must inform her treating physician immediately.
• Able to understand and willing to sign an IRB-approved written informed consent document (legally authorized representative permitted).

Exclusion Criteria:

• Leptomeningeal or metastatic involvement.
• Prior history of grade 3 or higher radiation necrosis that is at least possibly related to prior radiotherapy.
• Use of concurrent bevacizumab or other anti-VEGF-directed therapy during TMPRT is not allowed. If the patient is on bevacizumab, the patient needs to discontinue bevacizumab for at least 4 weeks prior to the start of TMPRT and remain stable. Other chemotherapy, immunotherapy, or target therapy can be used concurrently or adjuvantly at the discretion of treating physician.
• Medical contraindication to MRI (e.g., unsafe foreign metallic implants, incompatible pacemaker, inability to lie still for long periods, severe to end-stage kidney disease or on hemodialysis).
• Pregnant.