68Ga-HBED-CC-PSMA PET/CT Versus Histopathology In Primary Localized Prostate Cancer: A Voxel-Wise Comparison

Purpose: We performed a voxel-wise comparison of Ga-68-HBED-CC-PSMA PET/CT with prostate histopathology to evaluate the performance of Ga-68-HBED-CC-PSMA for the detection and delineation of primary prostate cancer (PCa). Methodology: Nine patients with histopathological proven primary PCa underwent Ga-68-HBED-CC-PSMA PET/CT followed by radical prostatectomy. Resected prostates were scanned by ex-vivo CT in a special localizer and histopathologically prepared. Histopathological information was matched to ex-vivo CT. PCa volume (PCa-histo) and non-PCa tissue in the prostate (NPCa-histo) were processed to obtain a PCa-model, which was adjusted to PET-resolution (histo-PET). Each histo-PET was coregistered to in-vivo PSMA-PET/CT data. Results: Analysis of spatial overlap between histo-PET and PSMA PET revealed highly significant correlations (p < 10(-5)) in nine patients and moderate to high coefficients of determination (R-2) from 42 to 82 % with an average of 60 +/- 14 % in eight patients (in one patient R-2 = 7 %). Mean SUVmean in PCa-histo and NPCa-histo was 5.6 +/- 6.1 and 3.3 +/- 2.5 (p = 0.012). Voxel-wise receiver-operating characteristic (ROC) analyses comparing the prediction by PSMA-PET with the non-smoothed tumor distribution from histopathology yielded an average area under the curve of 0.83 +/- 0.12. Absolute and relative SUV (normalized to SUVmax) thresholds for achieving at least 90 % sensitivity were 3.19 +/- 3.35 and 0.28 +/- 0.09, respectively. Conclusions: Voxel-wise analyses revealed good correlations of Ga-68-HBED-CC-PSMA PET/CT and histopathology in eight out of nine patients. Thus, PSMA-PET allows a reliable detection and delineation of PCa as basis for PET-guided focal therapies.