Magnetic resonance imaging-ultrasound fusion biopsy for prediction of final prostate pathology

Abstract

Purpose: We explored the impact of magnetic resonance imaging-ultrasound fusion prostate biopsy on the prediction of final surgical pathology.

Materials and methods: A total of 54 consecutive men undergoing radical prostatectomy at UCLA after fusion biopsy were included in this prospective, institutional review board approved pilot study. Using magnetic resonance imaging-ultrasound fusion, tissue was obtained from a 12-point systematic grid (mapping biopsy) and from regions of interest detected by multiparametric magnetic resonance imaging (targeted biopsy). A single radiologist read all magnetic resonance imaging, and a single pathologist independently rereviewed all biopsy and whole mount pathology, blinded to prior interpretation and matched specimen. Gleason score concordance between biopsy and prostatectomy was the primary end point.

Results: Mean patient age was 62 years and median prostate specific antigen was 6.2 ng/ml. Final Gleason score at prostatectomy was 6 (13%), 7 (70%) and 8-9 (17%). A tertiary pattern was detected in 17 (31%) men. Of 45 high suspicion (image grade 4-5) magnetic resonance imaging targets 32 (71%) contained prostate cancer. The per core cancer detection rate was 20% by systematic mapping biopsy and 42% by targeted biopsy. The highest Gleason pattern at prostatectomy was detected by systematic mapping biopsy in 54%, targeted biopsy in 54% and a combination in 81% of cases. Overall 17% of cases were upgraded from fusion biopsy to final pathology and 1 (2%) was downgraded. The combination of targeted biopsy and systematic mapping biopsy was needed to obtain the best predictive accuracy.

Conclusions: In this pilot study magnetic resonance imaging-ultrasound fusion biopsy allowed for the prediction of final prostate pathology with greater accuracy than that reported previously using conventional methods (81% vs 40% to 65%). If confirmed, these results will have important clinical implications.

Keywords: biopsy; magnetic resonance imaging; prostatectomy; prostatic neoplasms; ultrasonography.

Figure 1

68 year-old man with PSA 8.3 ng/ml who underwent multi-parametric MRI: (A) T2-weighted, (B) diffusion-weighted, and (C) dynamic contrast-enhanced imaging. He then underwent fusion biopsy (D). Mapping biopsy revealed Gleason 3+3, but (E) targeted biopsy revealed Gleason 4+5. Reduced from ×20. (F) Gleason score on whole-mount prostatectomy specimen was Gleason 4+3 with tertiary pattern 5. Fusion biopsy, which included the MRI-targeted region of interest, predicted the highest Gleason grade at final pathology. Reduced from ×1.