Metabolic Tumor Volume Is More Accurate Than SUV Metrics in PSMA-PET/CT Analysis Across Different PET/CT Scanners

A 66-year-old man with metastatic prostate cancer had PSMA avid local recurrence in the prostate on follow-up PSMA-PET/CT and MRI studies. The first PSMA-PET performed on Quadra scanner with concurrent PSA of 0.1 ng/mL had the highest SUVmax (64.9)/SUVmean (27.7) and TLG (98.3), but the lowest MTV (3.6 mL). The 2nd and 3rd PSMA-PET/CTs were obtained from the same DMI scanner. With concurrent PSA of 0.3 ng/mL, the 2nd PET showed higher SUVmax (43.3), SUVmean (18.7), and TLG (111.2), but lower MTV (5.9 mL) than the 3rd PET (SUVmax 38.5, SUVmean 12.2, TLG 107.4, MTV 8.4 mL) when concurrent PSA rose to 0.6 ng/mL. Regardless of the necessity of SUV harmonization across different PET scanners, this case illustrated that the MTV measurements appears in line with PSA change and independent with different scanners, thus might be more accurate in assess PSMA-avid disease.