Chemical-Shift-Encoded MRI for Active Bone Marrow Dosimetry in Radiopharmaceutical Therapy

This single-site, single-arm study will evaluate the accuracy of active bone marrow (ABM) segmentation with CSE-MRI by comparing to the established technique of FLT PET in patients with PSMA+ mCRPC who are scheduled to receive Lutetium-177 Prostate-Specific Membrane Antigen (177Lu-PSMA) (PLUVICTO®) Radiopharmaceutical Therapy (RPT) as standard of care. All standard of care testing, monitoring, and administration for 177Lu-PSMA RPT (PLUVICTO®) will be followed for this study.

Participants will receive 177Lu-PSMA RPT (PLUVICTO®) for a total of 6 doses, or until disease progression or unacceptable toxicity. Doses of 177Lu-PSMA RPT will be given at least 6 weeks apart. At the discretion of the prescribing physician, standard of care PSMA PET/MRI will be performed at any time during cycles 2-4, and also within 6 months of the final administration of 177Lu-PSMA RPT; during these scans, the CSE-MRI will also be acquired. Participants will be followed for 6 months following the final administration of 177Lu-PSMA RPT.

The primary endpoint is a calculation of the mean Dice similarity coefficient (DSC) between active bone marrow volumes derived from CSE-MRI and ¹⁸F-FLT PET across all enrolled patients. A mean DSC of ≥0.7 will indicate that CSE-MRI is a clinically acceptable alternative to FLT PET for identifying ABM.

With the exception of the research-related CSE-MRI and FLT PET scans, all assessments, laboratory tests, RPT, and imaging scans are standard of care.

Inclusion criteria

• Ability to understand and the willingness to sign a written informed consent document.
• Patients must be informed of the experimental nature of the study and its potential risks, and must sign institutional review board (IRB) approved consent form indicating such understanding.
• Individuals at least 18 years of age.
• Patients must have histologically or cytologically confirmed prostate cancer.
• Patients must be clinically deemed appropriate for standard of care Lu-177 PSMA RPT.
• Eastern Cooperative Oncology Group (ECOG) performance 0-2
• Patients must be able to comply with all study procedures, including having both the ability and willingness to lie flat for ≥ 30 minutes during imaging.

Exclusion criteria

• Patients receiving any concurrent therapy known to impact bone marrow (either stimulate or suppress the marrow, for example G-CSF).
• Patients treated with chemotherapy or 223Ra radiotherapy within 4 weeks.
• All acute toxic effects of any prior therapy (including surgery, radiation therapy, chemotherapy) must have resolved to a grade ≤ 2 according to National Cancer Institute Common Terminology Criteria for Adverse Events Version 5 (CTCAE).
• Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements per treating physician discretion.