A Pilot Study of [Ga-68]PSMA PET/MRI for the Assessment of PSMA-positive Tumors

Primary Objective The primary objective of this pilot imaging study is to determine the feasibility of using positron emission tomography/ magnetic resonance (PET/MR) with \[Ga-68\] prostate-specific membrane antigen (PSMA) for staging and treatment monitoring of PSMA expressing tumors. \[Ga-68\]PSMA PET/MR findings will be compared with standard of care imaging, patient follow up, and histopathology if available. \[Ga-68\]PSMA PET/MR will not be used to change the patients' treatment plan. Investigators will assess PET/MR test-retest reproducibility and compare baseline \[Ga-68\]PSMA PET/MR with PET/MR after initiation (within 2-6 weeks) of therapy and evaluate if \[Ga-68\]PSMA is a suitable biomarker for treatment monitoring and assessment of early treatment response. Secondary Objectives * To compare early changes in PET biomarker (\[Ga-68\]PSMA) tumor uptake with treatment response assessed at completion of therapy (prediction of treatment response). * To compare changes in MRI signal intensities (multi-parametric MRI) with treatment response assessed at completion of therapy. * To compare results from multi-parametric MR imaging with \[Ga-68\]PSMA uptake. * To assess combinations of quantitative PET and MRI metrics. Study Design Patients, who enroll in this study, will undergo a baseline \[Ga-68\]PSMA PET/MR to assess the level of \[Ga-68\]PSMA tumor uptake. Patients with positive \[Ga-68\]PSMA tumor uptake (defined as \[Ga-68\]PSMA uptake twice the background activity) who are receiving systemic therapy will undergo a further \[Ga-68\]PSMA PET/MR 2-6 weeks after start of treatment. Patients with positive \[Ga-68\]PSMA tumor uptake will also be offered to participate in a test- retest study with a 2nd \[Ga-68\]PSMA PET/MR prior to treatment. Patients will therefore undergo a maximum of three \[Ga-68\]PSMA PET/MR imaging procedures. The first two test-retest Ga-PSMA-PET/MRI will be performed on separate days to allow for radioactive decay. There will be no other (e.g. clinically indicated) PET scan performed on the same day of \[Ga-68\]PSMA-PET/MRI.