Improving Diagnosis of Primary Prostate Cancer With Combined ⁶⁸Ga-Prostate-Specific Membrane Antigen-HBED-CC Simultaneous PET and Multiparametric MRI and Clinical Parameters

Objective: The current study was designed to test the diagnostic performance of ⁶⁸Ga-prostate-specific membrane antigen (PSMA) PET and multiparametric MRI along with clinical parameters in the characterization of prostatic lesions.

Materials and methods: Eighty-two men with 63 malignant and 21 benign histologically proven prostate lesions who underwent complete clinical workup were included in this retrospective study. All patients underwent simultaneous whole-body ⁶⁸Ga-PSMA PET/MRI with dedicated multiparametric MRI. Prostate Imaging-Reporting and Data System (PI-RADS) version 2 assessment was used for predicting the likelihood of cancer. Uptake of ⁶⁸Ga-PSMA was recorded by adopting the copy-and-paste function of ROIs defined on MR images. ROC and combined ROC analyses were performed to test the diagnostic accuracy of individual and combined parameters. Spearman analysis was used to assess the correlations.

Results: PSMA uptake (maximum standardized uptake value) was significantly different among tumors with Gleason scores of 7, 8, and 9, with the lowest uptake in tumors with a score of 7 and the highest uptake in tumors with a score of 9. There was a significant difference between early- and delayed-phase PSMA uptake in malignant prostatic lesions (p < 0.01). Significant correlations were observed between delayed and differential PSMA uptake and PI-RADS category (p < 0.01 and < 0.01, respectively), digital rectal examination findings (p = 0.01 and < 0.01, respectively), Gleason score (p = 0.05 and < 0.05, respectively), and prostate-specific antigen levels (p = 0.01 for both). Combined ROC analysis of prostate-specific antigen levels, digital rectal examination findings, multiparametric MRI, and differential PSMA uptake were able to characterize prostatic lesions with a mean (± SD) AUC of 0.94 ± 0.03, compared with their individual AUCs of 0.77, 0.70, 0.82, and 0.88.

Conclusion: Gallium-68-PSMA PET combined with multiparametric MRI showed high diagnostic accuracy for prostate cancer diagnosis compared with either multiparametric MRI or PET alone or with clinical factors (e.g., digital rectal examination or prostate-specific antigen level) alone, and the combination further improves characterization of prostatic lesions.