Prostate cancer grading: the effect of stratification of needle biopsy Gleason Score 4 + 3 as high or intermediate grade

Abstract

To assess the discrepancy between needle biopsy (NB) and radical prostatectomy (RP) Gleason score (GS) in Irish men, specifically the influence of the stratification of GS 4 + 3 on overall levels of agreement, levels of discrepancy and kappa coefficients, as the GS assigned to prostate cancer NBs affects clinical decision-making and influences future therapeutic strategies. We reviewed retrospectively a database of the discrepancies between NB and RP Gleason grades (GG) from 2003 to 2008. All patients had clinically localized prostate cancer, and none had had neoadjuvant therapy. Grading of 206 NB specimens was compared with their corresponding RP specimens. The discrepancy rate between NB and RP GS was assessed for each combination of GG. Intermediate- (GS 7, defined as GS 3 + 4 alone vs GS 7) and high-grade (GS 4 + 3 and GS 8-10 vs GS 8-10) classifications were compared. The level of agreement and the kappa coefficient for each system was assessed. In NB, GS 6 was most frequently diagnosed (53%); after RP, GS 3 + 4 was most frequent (36%). In 42% of cases the exact GG remained unchanged after RP, increasing to 48% for GS 6 and GS 3 + 4. Overall 42% of cases showed an increase in their GG. In GS 6 NBs, the rate of increase in the primary GG or increase in the GS was 52%. Biopsy GS 6 and 3 + 4 showed the highest levels of agreement between NB and RP. Low-grade prostate cancer on NB was upgraded in 52% of cases; high-grade prostatic adenocarcinoma was downgraded in 27-77% of cases depending on the grading system used. Classification of high-grade prostate cancer as GS 4 + 3 and GS 8-10 results in higher levels of agreement between NB and RP GS. Reliable identification of well differentiated prostatic adenocarcinoma in NB specimens represents an ongoing diagnostic challenge, necessitating careful preoperative consideration of the definitive grade of a patient's disease.