68Ga-PSMA PET/CT Detects the Location and Extent of Primary Prostate Cancer.

Abstract

We evaluated the accuracy of PET/CT with ⁶⁸Ga-PSMA-HBED-CC-a ⁶⁸Ga-conjugated ligand of human prostate-specific membrane antigen (PSMA)-to localize cancer in the prostate and surrounding tissue at initial diagnosis. Twenty-one patients with biopsy-proven prostate cancer underwent ⁶⁸Ga-PSMA-HBED-CC (⁶⁸Ga-PSMA) PET/CT at a median of 4 d (range, 0-47 d) before radical prostatectomy. Based on a 6-segment model, the Gleason score and proportion of tumor tissue within each segment (segmental tumor burden, or STB) as determined by histopathology (STB_HP) were correlated with SUV_max and STB as determined by different SUV cutoffs for ⁶⁸Ga-PSMA PET (STB_PET1-6). Furthermore, the involvement of seminal vesicles and other extracapsular extension were assessed by histopathology and PET/CT. Histopathology-positive segments (n = 100 of 126; 79%) demonstrated a significantly higher mean ± SD SUV_max (11.8 ± 7.6) than histopathology-negative segments (4.9 ± 2.9; P < 0.001). Receiver-operating-characteristic analysis revealed an optimal SUV_max cutoff of 6.5 for discrimination of histopathology-positive segments from histopathology-negative segments (area under the curve, 0.84; P < 0.001), which gave 67% sensitivity, 92% specificity, a 97% positive predictive value, a 42% negative predictive value, and 72% accuracy. STB_PET3 as determined by (2 × blood SUV) + (2 × SD) correlated best with STB_HP (Pearson ρ = 0.68; P < 0.001; mean difference ± SD, 19% ± 15%). PET/CT correctly detected invasion of seminal vesicles (n = 11 of 21 patients; 52%) with 86% accuracy and tumor spread through the capsule (n = 12; 57%) with 71% accuracy. ⁶⁸Ga-PSMA PET/CT accurately detected the location and extent of primary prostate cancer. Our preliminary findings warrant further investigation of ⁶⁸Ga-PSMA PET/CT in conjunction with needle biopsy.