Gleason scores provide more accurate prognostic information than grade groups

Abstract

Prostate cancer grade is currently often reported both by Gleason scores and by grouping of the scores into five so-called International Society of Urological Pathology (ISUP) grades (also known as grade groups). Using population-based registry data from 172,112 men diagnosed with prostate cancer on needle biopsy, we recently investigated the outcome of Gleason score 8-10 prostate cancer with death due to prostate cancer and death from any cause as endpoints. There was a prognostic heterogeneity between Gleason scores 3+5, 4+4 and 5+3 (ISUP grade 4) and between Gleason scores 4+5, 5+4 and 5+5 (ISUP grade 5). This heterogeneity was lost when the grades collapsed into ISUP grades 4 and 5, respectively. On the other hand, there was also a prognostic overlap between these ISUP grades. The outcome of Gleason score 5+3 and 4+5 cancers was very similar. The prostate-specific mortality of Gleason scores 5+3 and 4+5 was 0.32 (95% confidence interval 0.27-0.36) and 0.30 (0.29-0.31), respectively, after 5 years and 0.44 (0.39-0.49) and 0.45 (0.44-0.46), respectively, after 10 years. The findings emphasise the importance of reporting the Gleason grades and scores for more accurate prognostic information of highly heterogeneous high-grade prostate cancers. It also questions the clinical value of the current recommendations of grouping of Gleason scores into ISUP grades or grade groups.

Keywords: Gleason grade; mortality; needle biopsy; prostate cancer.