Imaging Discordance Between [⁶⁸Ga]-PSMA PET and [¹⁷⁷Lu]-PSMA SPECT in mCRPC.

Area of Science:

• Oncology
• Nuclear Medicine
• Radiopharmaceutical Therapy

Background:

• Prostate-specific membrane antigen (PSMA) PET/CT is standard for selecting patients for [¹⁷⁷Lu]-PSMA radioligand therapy (LuPSMA RLT).
• Differences in pharmacokinetics and biodistribution between diagnostic ([⁶⁸Ga]-PSMA-11) and therapeutic ([¹⁷⁷Lu]-PSMA-617) ligands can lead to discordant imaging findings.
• Discordance may result in underestimation of disease burden and exclusion of eligible patients for LuPSMA RLT.

Purpose of the Study:

• To highlight the clinical significance of integrating post-therapy LuPSMA imaging and FDG PET/CT in advanced prostate cancer management.
• To illustrate the importance of personalized treatment strategies for PSMA-negative/FDG-avid lesions.

Main Methods:

• Case report of metastatic castration-resistant prostate cancer (mCRPC).
• Utilized PSMA PET/CT for initial staging and [¹⁷⁷Lu]-PSMA imaging post-therapy.
• Incorporated FDG PET/CT for characterization of discordant lesions.
• Administered complementary stereotactic body radiotherapy (SBRT).

Main Results:

• A PSMA-negative adrenal lesion on initial PET demonstrated significant LuPSMA uptake post-therapy.
• This lesion was subsequently confirmed as FDG-avid.
• Metabolic remission was achieved with complementary SBRT.

Conclusions:

• Post-therapy LuPSMA imaging is crucial for accurate disease characterization, especially in cases of discordance with pre-therapy scans.
• Integrating FDG PET/CT with LuPSMA imaging aids in managing PSMA-negative/FDG-avid lesions in advanced prostate cancer.
• Personalized management combining systemic therapy, advanced imaging, and targeted radiotherapy is essential for optimizing outcomes in mCRPC.