Combination MRI-targeted and systematic prostate biopsy may overestimate gleason grade on final surgical pathology and impact risk stratification.

ABSTRACT

PURPOSE: Gleason grade (GG) on prostate biopsy is important for risk stratification and clinical decision making. Multiparametric MRI (mpMRI) improved detection of clinically significant disease and some studies suggest that MRI-fusion biopsy combined with systematic biopsy results in fewer upgrades on final surgical pathology. However, the downgrade rate is unclear and there is controversy in the literature. The objectives of this study are to assess the concordance of combination biopsy with final surgical pathology, and furthermore, to specifically determine downgrade rates. MATERIALS AND METHODS: In our institutional mpMRI-ultrasound fusion biopsy database, 173 underwent targeted and systematic biopsy followed by radical prostatectomy (RP). GG on targeted, systematic and combination (targeted and systematic) biopsy were compared with GG on RP. Concordance rates between biopsy types were compared with the McNemar test. Proportion of GG upgrade or downgrade at the time of RP was also evaluated. RESULTS: Surgical pathology was concordant with 44.5% of systematic biopsies, 46.8% of targeted biopsies, and 56.7% of combination biopsies. Combination biopsy significantly overestimated the final GG on RP compared to systematic biopsy (16.8% vs. 8.7% RR 1.93, 95% CI 1.36-2.75, P < 0.001). Downgrade rate from unfavorable to favorable intermediate-risk disease was 46.2%, and from high-risk to intermediate-risk disease was 45.1%. CONCLUSIONS: Combination (targeted and systematic) biopsy is associated with the highest concordance rate between biopsy and RP pathology when compared with systematic or targeted biopsy alone. However, targeting MRI lesions and therefore the higher risk components, may at times overestimate the final surgical pathology which can result in overtreatment of what may truly be less aggressive disease.