Inclusion Criteria

• Age > 18 years old.
• ECOG PS < 3.
• Histologically confirmed or radiographic evidence of recurrent/progressive high-grade glioma after treatment with bevacizumab.
• History of radiation therapy to the brain for prior diagnosis of glioma.
• Planned radiation treatments at Mayo Clinic Rochester.
• Provide informed written consent.
• Willing to sign consent onto the Mayo Clinic Radiotherapy Patient Outcomes Registry and Biobanking study, IRB number 15-000136 (blood draw optional).
• Willing to return to enrolling institution for follow-up during Active Monitoring Phase of the study.

Exclusion Criteria

• More than one prior course of radiotherapy or prior prescription doses exceeding 60 Gy to target volumes.
• Unable to undergo MRI scans with contrast.
• Unable to undergo an 18F-DOPA-PET scan (e.g., Parkinson's Disease, taking anti dopaminergic, or dopamine agonist medication or less than 6 half-lives from discontinuance of dopamine agonists).
  • Note: Other potentially interfering drugs: amoxapine, amphetamine, benztropine, buproprion, buspirone, cocaine, mazindol, methamphetamine, methylphenidate, norephedrine, phentermine, phenylpropanolamine,selegiline, paroxetine, citalopram, and sertraline). If a patient is on any of these drugs, list which ones on the On-Study form.
• Any of the following:
  • Pregnant women;
  • Nursing women;
  • Men or women of childbearing potential who are unwilling to employ adequate contraception.