The modified ISUP system improves concordance between biopsy and prostatectomy tumour grade.

OBJECTIVES: To assess the concordance between biopsy and radical prostatectomy (RP) specimens using the 2005 Gleason Score (GS) and the ISUP 2014/ WHO 2016 modified GS system, accounting for the introduction of transperineal biopsy and pre-biopsy multiparametric MRI (mpMRI). PATIENTS AND METHODS: Between 2002 and 2019, we identified 2431 patients with paired biopsy and RP histopathology, from a prospectively recorded and maintained prostate cancer database. Biopsy specimens were graded according to the 2005 GS or ISUP 2014 modified GS system, according to the year of diagnosis. Multivariable logistic regression analysis was conducted to retrospectively assess the impact of PSA, PSA density, age, pre-biopsy mpMRI, and biopsy method, on the rate of upgraded disease. The Kappa coefficient was used to establish the degree of change in concordance between groups. RESULTS: Overall, 24% of patients had upgraded disease and 8% of patients had downgraded disease when using the updated ISUP 2014 criteria. Agreement in the updated ISUP 2014 cohort was 68% compared with 55% in the 2005 GS group, which was validated by a kappa co-efficient that was good (k=0.5 ± 0.4) and poor (k=0.3 ± 0.1), respectively. In multivariable models, a change in ISUP grading system independently improved overall disease concordance (p=0.02), and there were no other co-segregated patient or pathological factors such as PSA, total number of cores, maximum cancer length, biopsy route or the use of mpMRI that impacted this finding. CONCLUSION: The 2014 ISUP modification of the Gleason grading system improves overall concordance between biopsy and surgical specimens, and thus allows more accurate prognostication and management in high-grade disease, independent of more extensive prostate sampling and the use of mpMRI.