Comparison of hybrid ⁶⁸Ga-PSMA-PET/CT and ^99mTc-DPD-SPECT/CT for the detection of bone metastases in prostate cancer patients: Additional value of morphologic information from low dose CT.

Abstract

This study compared ⁶⁸Gallium-prostate-specific-membrane-antigen based Positron-emission-tomography (⁶⁸Ga-PSMA-PET) and ^99metastabletechnetium-3,3-diphospho-1,2-propanedicarbonacid (^99mTc-DPD-SPECT) in performing skeletal staging in prostate cancer (PC) patients and evaluated the additional value of the information from low-dose-computed tomography (CT). In this retrospective study, 54 patients who received ⁶⁸Ga-PSMA-PET/CT and ^99mTc-DPD-SPECT/CT within 80 days were extracted from our database. Osseous lesions were classified as benign, malignant or equivocal. Lesion, region and patient based analysis was performed with and without CT fusion. The reference standard was generated by defining a best valuable comparator (BVC) containing information from all available data. In the patient based analysis, accuracies measured as "area-under-the-curve" (AUC) for ⁶⁸Ga-PSMA-PET, ^99mTc-SPECT, ⁶⁸Ga-PSMA-PET/CT and ^99mTc-SPECT/CT were 0.97-0.96, 0.86-0.83, 1.00 and 0.83, respectively (p<0.05) (ranges = optimistic vs. pessimistic view). Region based analysis resulted in the following sensitivities and specificities: 91.8-97.7%, 100-99.5% (PET); 61.2-70.6%, 99.8-98.3% (SPECT); 97.7%, 100% (PET/CT), 69.4% and 98.3% (SPECT/CT) (p<0.05). The amount of correct classifications of equivocal lesions by CT was significantly higher in PET (100%) compared to SPECT (52.4%) (p<0.05). ⁶⁸Ga-PSMA-PET outperforms ^99mTc-DPD-SPECT in detecting bone metastases in PC patients. Additional information from low-dose-CT resulted in a significant reduction in equivocal lesions in both modalities, however ⁶⁸Ga-PSMA-PET benefited most. • Ga-PSMA-PET outperforms ^99m Tc-DPD-SPECT in skeletal staging in prostate cancer patients • Proportion of equivocal decisions was significantly reduced by CT-fusion in both modalities • Ga-PSMA-PET benefits more from CT information, compared to ^99m Tc-DPD-SPECT.