LAUSR

Purpose Prostate cancer (PCa) commonly metastasizes to the bones. There are several radionuclide techniques for imaging PCa skeletal metastases. We aimed to compare the lesion detection rate of [ 68 Ga]Ga-PSMA-11 PET/CT, [ 68 Ga]Ga-NODAGA-zoledronate ([ 68 Ga]Ga-NODAGA ZOL ) PET/CT, and [ 99m Tc]Tc-MDP bone scan in the assessment of bone metastases in patients with advanced PCa. Methods We prospectively recruited two cohorts of patients (staging and re-staging cohorts) with advanced prostate cancer. The staging cohort was treatment-naïve PCa patients who showed skeletal metastases on bone scan. These patients were subsequently imaged with [ 68 Ga]Ga-PSMA-11 PET/CT and [ 68 Ga]Ga-NODAGA ZOL PET/CT. Re-staging cohort was patients who were previously treated with PSMA-based radioligand therapy and were experiencing PSA progression. The re-staging cohort was imaged with [ 68 Ga]Ga-PSMA-11 PET/CT and [ 68 Ga]Ga-NODAGA ZOL PET/CT. We performed a per-patient and per-lesion analysis of skeletal metastases in both cohorts and made a comparison between scan findings. Results Eighteen patients were included with a median age of 68 years (range = 48–80) and a median Gleason score of 8. There were ten patients in the staging cohort with a median PSA of 119.26 ng/mL (range = 4.63–18,948.00) and eight patients in the re-staging cohort with a median PSA of 48.56 ng/mL (range = 6.51–3175.00). In the staging cohort, skeletal metastases detected by [ 68 Ga]Ga-PSMA-11 PET/CT, [ 68 Ga]Ga-NODAGA ZOL PET/CT, and bone scan were 322, 288, and 261, respectively, p  = 0.578. In the re-staging cohort, [ 68 Ga]Ga-PSMA-11 PET/CT and [ 68 Ga]Ga-NODAGA ZOL PET/CT detected 152 and 191 skeletal metastases, respectively, p  = 0.529. In two patients with negative [ 68 Ga]Ga-PSMA-11 PET/CT findings, [ 68 Ga]Ga-NODAGA ZOL detected one skeletal metastasis in one patient and 12 skeletal metastases in the other. Conclusion In patients with advanced prostate cancer, [ 68 Ga]Ga-PSMA-11 PET/CT may detect more lesions than [ 68 Ga]Ga-NODAGA ZOL PET/CT and [ 99m Tc]Tc-MDP bone scan for the staging of skeletal metastases. In patients who experience PSA progression on PSMA-based radioligand therapy, [ 68 Ga]Ga-NODAGA PET/CT is a more suitable imaging modality for the detection of skeletal lesions not expressing PSMA. In the setting of re-staging, [ 68 Ga]Ga-NODAGA ZOL PET/CT may detect more lesions than [ 68 Ga]Ga-PSMA-11 PET/CT.