PURPOSE: To determine if 18F-choline PET/mpMRI can improve the specificity of mpMRI for Gleason ≥3+4 prostate cancer.
METHODS: Multi-parametric prostate MRI (mpMRI) and 18F-choline PET/CT were performed prior to targeted and systematic prostate biopsy in a prospective IRB-approved clinical trial of 56 consented subjects who had ≥1 low-, intermediate-, or high-risk target(s) on mpMRI (trial initiated prior to PI-RADS v2) with clinical need for prostate biopsy. The 18F-choline uptake of MRtargets was normalized by mirrored background (target-to-background ratio [TBR]) and a TBR >1.583 indicated a positive 18F-choline result. Prostate biopsies were performed after registration of real-time transrectal ultrasound (TRUS) with T2-weighted MRI. A mixed-effects logistic regression model followed by area under the curve (AUC) estimation was used to measure the performance of mpMRI and 18F-choline PET/mpMRI to diagnose Gleason ≥3+4 cancer.
RESULTS: Ninety lesions (40 low-risk, 30 intermediate-risk, 20 high-risk; 29 Gleason ≥3+4 cancers) were identified by mpMRI. mpMRI accuracy was 69.9% (AUC=0.73) targeting intermediate- and high-risk lesions. The AUC significantly improved (p <0.005) after incorporation of 18Fcholine TBR data in two scenarios: a) “hybrid” 18F-choline PET/mpMRI, where high-risk mpMRI lesions and low- or intermediate-risk mpMRI lesions with 18F-choline TBR >1.583 are targeted (AUC=0.91), and b) “stepwise PET/mpMRI”, where mpMRI is performed first (targeting high-risk lesions only) and 18F-choline PET TBR >1.583 is used only for risk-stratification of intermediate-risk lesions (AUC=0.93).
CONCLUSIONS: 18F-choline PET/mpMRI improves the identification of Gleason ≥3+4 prostate cancer compared to mpMRI alone, with the principal effect being improved risk-stratification of intermediate-risk mpMRI lesions.
