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.

Inclusion criteria

• Patients with PSMA-positive tumors including prostate cancer, breast cancer, lung cancer, and other tumor types know to express PSMA
• Patients able to tolerate PET/MRI scans
• Informed consent must be given and signed

Exclusion criteria

• Subjects who do not meet the above mentioned inclusion criteria
• Subjects who refuse to give and/or sign the informed consent
• Patients who have a history of serious adverse events related to a previous MRI or PET/CT
• Patients who are unable to undergo MRI scanning due to exclusion by institutional MRI restriction policies as mentioned in the standard institutional MRI informed consent form
• Patients who are currently pregnant or breast feeding. A pregnancy test within 72 hours of the first PET/MRI will be performed.
• Anti-cancer treatment (chemotherapy and/or radiation therapy) within the last 2 weeks.
• Renal insufficiency: elevated Creatinine and/or Glomerular Filtration Rate (GFR)<40ml/min/1.7sqm (exclusion criterion only for contrast enhanced MRI)
• Patients with a known allergy against any component of the contrast enhancing MR agent will not receive MR contrast agents. (exclusion criterion only for contrast enhanced MRI)