Evaluating F-18-PSMA-1007-PET in primary prostate cancer and comparing it to multi-parametric MRI and histopathology

Background: PSMA-PET is a novel imaging modality for the staging of prostate cancer (PCa). While there are several PSMA ligands available, F-18-PSMA-1007 is particularly of interest as it is not renally excreted and therefore does not impair the imaging of the pelvic area. Hence, this study aimed to investigate the F-18-PSMA-1007-PET for the primary staging of PCa and compared it to multi-parametric (mp) MRI and histopathology.

Methods: A retrospective study was performed of men with intermediate and high-risk PCa patients that underwent a F-18-PSMA-1007-PET after mpMRI with subsequent MR-guided target biopsy (MRGB). Suspicious mpMRI lesions and F-18-PSMA-1007-PET were simultaneously reviewed on both a per patient and per-lesion basis. Results were subsequently evaluated with histopathological outcome of MRGB, and if performed, the radical prostatectomy specimen.

Results: A total of 66 suspicious mpMRI lesions were identified in 53 patients and underwent MRGB. Two lesions had a maximum standardized uptake value (SUV_max) less than the mean SUV_max of healthy prostate tissue and were considered as non-PSMA-expressing. All PSMA avid tumors had higher SUV_max than the mean SUV_mean of the bladder/urine, therefore all lesions were clearly distinguishable in the pelvic area. Twenty-three patients received a radical prostatectomy of which the histopathology specimens were evaluated. F-18-PSMA-1007-PET/CT correctly staged seminal vesicle invasion (i.e. pT3b) more often than mpMRI (90 vs. 76%), whereas mpMRI more accurately detected extracapsular extension (i.e. pT3a) compared to F-18-PSMA-1007-PET (90% vs 57%).

Conclusions: The present study of a selected cohort suggest that dual imaging with mpMRI and F-18-PSMA-1007-PET may improve staging of primary PCa. F-18-PSMA-1007-PET/CT had low renal clearance, which could assist the evaluation of tumors in proximity of the bladder.