Performance of PI-RADS v2 assessment categories assigned prior to MR-US fusion biopsy in a new fusion biopsy program

Abstract

Objective: To validate the performance of PI-RADS v2 for detection of clinically significant prostate cancer (csPca, Gleason ≥7) within the context of a new fusion biopsy program.

Material and methods: Patients with a PI-RADS v2 assessment category assigned on pre-biopsy mpMRI between March 2015 and November 2017 were identified. Diagnostic performance of PI-RADS v2 was calculated using fusion biopsy results as reference standard using receiver operating characteristic curve analysis. Patient and lesion characteristics were analyzed with one-way ANOVA and Wilcoxon rank sum test.

Results: Of 83 patients with 175 lesions, 115/175 (65.7%) were benign, 21/175 (12%) were Gleason 6, and 39/175 (22.3%) were Gleason ≥7. csPCa rates were 0% (0/5) for PI-RADS 1, 7.4% (2/27) for PI-RADS 2, 5.8% (3/52) for PI-RADS 3, 31.2% (24/77) for PI-RADS 4, and 71.4% (10/14) for PI-RADS 5 (p < 0.0001). For prediction of csPCa, patient-level AUC was 0.68 and lesion-level AUC was 0.77. Biopsy threshold of PI-RADS ≥3 was 92.6% sensitive and 22.1% specific. A threshold of PI-RADS ≥4 was 87.2% sensitive and 58.1% specific. Rate of csPca detection on concurrent standard 12 core biopsy only was 6.7%.

Conclusion: PI-RADS v2 assessment categories assigned prior to biopsy predict pathologic outcome reasonably well in a new prostate fusion biopsy program. Biopsy threshold of PI-RADS ≥3 is highly sensitive. A threshold of ≥4 increases specificity but misses some csPCa.

Keywords: Fusion biopsy; Multiparametric MRI of prostate; PI-RADS version 2; Prostate cancer.