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

PSMA PET/CT is commonly used for selecting candidates for [¹⁷⁷Lu]-PSMA radioligand therapy (LuPSMA RLT). However, discrepancies may occur due to pharmacokinetic and biodistribution differences between [⁶⁸Ga]-PSMA-11 and [¹⁷⁷Lu]-PSMA-617 ligands. Such discordance risks underestimating disease burden and excluding eligible patients. We present a case of metastatic castration-resistant prostate cancer (mCRPC) in whom a PSMA-negative adrenal lesion on PET exhibited significant LuPSMA uptake post-therapy and was subsequently confirmed as FDG-avid. Complementary stereotactic body radiotherapy (SBRT) achieved metabolic remission. This case highlights the clinical significance of integrating post-therapy LuPSMA imaging and FDG PET/CT with systemic treatment to ensure accurate disease characterization and personalized management of PSMA-/FDG+ lesions in advanced prostate cancer.