Diagnostic discordance in outside prostate biopsies: Implications for active surveillance patient selection.

PURPOSE: Gleason grade group (GG) concordance between prostate biopsy and radical prostatectomy (RP) is critical for treatment planning, particularly for active surveillance (AS). We compared GG concordance, upgrade rates, and AS misclassification between institutional and outside biopsies and evaluated the impact of pathologic re-evaluation. MATERIALS AND METHODS: In this propensity score-matched cohort study, 3,744 patients (1,872 institutional and 1,872 outside biopsies) who underwent RP were analyzed. Outside biopsies were stratified by re-evaluation status (re-evaluated, n=570; not re-evaluated, n=1,302). Primary outcomes included overall GG concordance, clinically significant upgrade (≥2 GG), and AS misclassification (biopsy GG 1 to RP ≥GG 3). Agreement was assessed using weighted kappa statistics, and predictors of upgrade were identified by multivariable logistic regression. RESULTS: Overall GG concordance was 44.7%. Institutional biopsies showed the highest concordance (47.8%) compared to outside biopsies with (45.3%) and without re-evaluation (40.0%) (p<0.001). Among biopsy GG 1 patients, AS misclassification to ≥GG 3 occurred in 9.6% of institutional biopsies, compared to 27.0% of outside re-evaluated biopsies and 20.0% of outside non-re-evaluated biopsies (p<0.0001). Outside biopsy source (odds ratio [OR] 1.351, p=0.013) and absence of re-evaluation (OR 1.451, p=0.028) were identified as independent predictors of GG upgrade. CONCLUSIONS: Outside prostate biopsies exhibit 2.1- to 2.8-fold higher AS misclassification rates compared to institutional biopsies. Pathologic re-evaluation provides only modest improvement and does not eliminate upgrade risk, supporting systematic second-opinion review and careful confirmation before AS enrollment.