During the participant's tumor biopsy or resection, the neurosurgeon will perform maximal safe resection, as per standard clinical practice, and allocate nine tissue specimens (three from the core of the tumor and six from the tumor-brain interface) for UR-ddPCR testing. If both core and tumor-brain interface samples test positive and further removal is judged safe, the neurosurgeon may perform additional resection and obtain final specimens from the positive sites before concluding the surgery. Up to 15 tissue specimens may be collected and tested during the procedure. Postoperative care and clinical follow-up will proceed per standard of care.

The investigational UR-ddPCR assay will be performed on collected tissue specimens during the participant's scheduled surgical visit.

PFS is defined as the time from surgery to the time of the first MRI demonstrating radiographic progression (using Response Assessment in Neuro-Oncology [RANO] criteria) or death due to any cause (whichever occurs earlier).

OS is defined as the time from surgery to the time of death due to any cause (whichever occurs earlier).

Assessed via MRI.