18F-Choline PET/mpMRI for Detection of Clinically Significant Prostate Cancer: Part 1. Improved Risk Stratification for MRI-Guided Transrectal Prostate Biopsies

A prospective single-arm clinical trial was conducted to determine whether 18 F-choline PET/mpMRI can improve the specificity of multiparametric MRI (mpMRI) of the prostate for Gleason 314 prostate cancer. Methods: Before targeted and systematic prostate biopsy, mpMRI and 18 F-choline PET/CT were performed on 56 evaluable subjects with 90 Likert score 3-5 mpMRI target lesions, using a 18 F-choline target-to-background ratio of greater than 1. 58 to indicate a positive 18 F-choline result. Prostate biopsies were performed after registration of real-time transrectal ultrasound with T2weighted MRI. A mixed-effects logistic regression was applied to measure the performance of mpMRI (based on prospective Likert and retrospective Prostate Imaging Reporting and Data System, version 2 PI-RADS, scores) compared with 18 F-choline PET/mpMRI to detect Gleason 314 cancer. Results: The per-lesion accuracy of systematic plus targeted biopsy for mpMRI alone was 67. 8% (area under receiver-operating-characteristic curve AUC, 0. 73) for Likert 4-5 and 70. 0% (AUC, 0. 76) for PI-RADS 3-5. Several PET/MRI models incorporating 18 F-choline with mpMRI data were investigated. The most promising model selected all high-risk disease on mpMRI (Likert 5 or PI-RADS 5) plus low-and intermediate-risk disease (Likert 4 or PI-RADS 3-4), with an elevated 18 F-choline targetto-background ratio greater than 1. 58 as positive for significant cancer. Using this approach, the accuracy on a per-lesion basis significantly improved to 88. 9% for Likert (AUC, 0. 90; P, 0. 001) and 91. 1% for PI-RADS (AUC, 0. 92; P, 0. 001). On a per-patient basis, the accuracy improved to 92. 9% for Likert (AUC, 0. 93; P, 0. 001) and to 91. 1% for PI-RADS (AUC, 0. 91; P 5 0. 009). Conclusion: 18 F-choline PET/ mpMRI improved the identification of Gleason 314 prostate cancer compared with mpMRI, with the principal effect being improved risk stratification of intermediate-risk mpMRI lesions.