This is a companion imaging study that plans to enroll adult subjects with recurrent glioblastoma that meet the eligibility criteria for a treatment trial entitled A phase II study evaluating the efficacy and safety of niraparib and tumor-treating fields in recurrent glioblastoma, IRB 832694/UPCC 03319. IRB 832694 is a study of niraparib, a brain-penetrant PARP inhibitor, in combination with tumor treating fields (TTFields) for recurrent GBM. The companion treatment trial has two cohorts. In Cohort A, subjects that do not have a clinical indication for surgical resection of the recurrent tumor will start TTFields therapy 5-7 days prior to starting oral niraparib (a PARP inhibitor). In Cohort B, subjects who have a clinical indication for surgical resection of the recurrent tumor will receive TTFields therapy for 5-7 days prior to planned surgical resection, undergo resection, and then resume TTFields therapy and initiate niraparib post-operatively. Sub-Investigators in the oncology team will help to identify subjects for the imaging study. Patients may participate in this study if they are at least 22 years of age. Up to 12 subjects will be approached to participate in this companion imaging protocol to undergo brain imaging with the novel radiopharmaceutical [18F]Fluorthanatrace ([18F]FTT) which measure PARP-1 activity using a Positron Emission Tomography (PET/CT) scan. Participants will undergo up to three [18F]FTT PET/CT scans at the following time points: Baseline: Subjects from either cohort may agree to undergo a baseline [18F]FTT PET/CT prior to the start of TTFields therapy to measure baseline FTT uptake. This scan is not required and may be omitted at the discretion of the investigator or based on subject availability or scheduling constraints for the scan in regards to the start of the treatment study. We anticipate that approximately 75% of subjects will complete this scan. Post-TTFields: Subjects from both cohorts will undergo an [18F]FTT PET/CT scan 3-7 days after initiation of TTFields therapy and before surgical resection or initiation of niraparib. This scan will measure the FTT uptake after TTFields therapy is initiated. This scan is required. Post-PARPi: Subjects from Cohort A may agree to undergo an post-therapy [18F]FTT PET/CT scan 1-21 days after the initiation of niraparib to collect pilot data on the changes in FTT uptake after TTFields and niraparib combination therapy. This scan is not required and may be omitted at the discretion of the investigator or based on subject availability.

You may be eligible for this study if you meet the following criteria:

• Conditions: Medical Research
• Age: 99 years or below
• Gender: All