The purpose of this study is to find out whether 68Ga-PSMA-11 PET/CT is effective in assessing tumor uptake (tumor activity seen in cancerous tissue) in participants with high-grade glioma/HGG or brain metastases.

Inclusion Criteria:

• Ability to understand and the willingness to sign (or their legally acceptable representative (LAR) must sign) a written informed consent document
• Adults ≥ 18 years old
• Suspicion for or histologically or cytologically confirmed and previously treated HGG or brain metastases from a primary extracranial malignancy
• Lesion size ≥ 1 cm (for the lesion to be biopsied)
• ECOG performance status ≤ 2 (Karnofsky ≥ 60%)
• Planned to undergo biopsy/resection of brain lesion

Exclusion Criteria:

• Inability to undergo a PET scan (e.g., claustrophobia or noncompatible implant in case PET/MR is performed)
• Pregnant or nursing female. All women of childbearing potential must have a documented negative serum or urine pregnancy test <1 week before study.
• Uncontrolled, intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiacarrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements.
• Patients with severe allergy to both iodinated and gadolinium contrast.

Memorial Sloan Kettering Cancer Center supports the international committee of medical journal editors (ICMJE) and the ethical obligation of responsible sharing of data from clinical trials. The protocol summary, a statistical summary, and informed consent form will be made available on clinicaltrials.gov when required as a condition of Federal awards, other agreements supporting the research and/or as otherwise required. Requests for deidentified individual participant data can be made beginning 12 months after publication and for up to 36 months post publication. Deidentified individual participant data reported in the manuscript will be shared under the terms of a Data Use Agreement and may only be used for approved proposals. Requests may be made to: crdatashare@mskcc.org.