Assessment of skeletal metastasis in prostate cancer staging: an intra-individual comparison of68Ga-PSMA PET/CT,68Ga-NODAGA-Zoledronate PET/CT, and99mTc-MDP bone scan

1256 Background: Zoledronate is a bisphosphonate that accumulates at sites of high bone turnover. Radiolabeled Zoledronate has been successfully demonstrated in clinical imaging of skeletal metastasis. 68Ga-NODAGA-Zoledronate PET/CT with 68Ga-PSMA PET/CT has, in recent times, joined 99mTc-MDP bone scan as radionuclide options for the assessment of skeletal metastasis. Bone is a common site of prostate cancer (PCa) metastasis. We aimed to compare the diagnostic ability of 68Ga-PSMA PET/CT, 68Ga-NODAGA-Zoledronate PET/CT, and 99mTc-MDP bone scan in the detection of skeletal metastases in the staging of treatment-naive men with intermediate- to high-risk PCa. Methods: Men with newly diagnosed adenocarcinoma of the prostate gland were prospectively recruited to undergo, within four weeks, imaging with 68Ga-PSMA PET/CT, 68Ga-NODAGA-Zoledronate PET/CT, and 99mTc-MDP bone scan for the assessment of skeletal metastasis. Two experienced readers independently performed image analysis. Per patient and per lesion analyses were done and compared between imaging tests. The SUVmax of the most intense lesion was compared between 68Ga-PSMA PET/CT and 68Ga-NODAGA-Zoledronate PET/CT. Results: Ten men were included with median age, Gleason score and PSA of 68.5 years (Interquartile range, IQR=63 - 74), 8 (IQR=8-9) and 119.29 ng/mL (IQR=25 - 280.58), respectively. On per-patient analysis, skeletal metastasis was detected in all patients on all three imaging tests. On a per lesion analysis, 68Ga-PSMA PET/CT identified more lesions (n=213 skeletal metastases) compared with 68Ga-NODAGA-Zoledronate PET/CT (n=174 skeletal metastases) and 99mTc-MDP bone scan (n=153 skeletal metastases), p=0.355. The mean SUVmax of the most intense lesion was 20.26 ± 7.56 for 68Ga-PSMA PET/CT compared with 14.82 ± 7.93 for 68Ga-NODAGA-Zoledronate PET/CT, p=0.227. Conclusion: On a per-patient basis, 68Ga-PSMA PET/CT, 68Ga-NODAGA-Zoledronate PET/CT, and 99mTc-MDP bone scan have a comparable performance for the detection of skeletal metastases in men with intermediate- to high-risk PCa. On a per lesion analysis, the seeming better performance of 68Ga-PSMA PET/CT in detecting more skeletal metastases than 68Ga-NODAGA-Zoledronate PET/CT and 99mTc-MDP bone scan did not reach statistical significance.