The 2019 International Society of Urological Pathology (ISUP) Consensus Conference on Grading of Prostatic Carcinoma.

In Reply: We thank Drs Epstein and Hirsch for their interest in the 2019 International Society of Urological Pathology (ISUP) Consensus Statement on Grading of Prostate Cancer.1 For >15 years, ISUP has been serving the global genitourinary community through seminars, consensus meetings, and publishing practical guidelines and recommendations, many of which were co-organized or co-authored by Dr Epstein. In 2018, the Genitourinary Pathology Society (GUPS) was founded and also published recommendations on prostate cancer grading.2 The recommendations of ISUP and GUPS are mostly similar, with minimal discordance3–5 but comparisons such as the above letter of Drs Epstein and Hirsch stressing consensus divergence from only one point of view, and also omitting significant issues (eg, the use, vs. absence, of a voting approach and consensus criteria) may detract from conveying widespread confidence in prostate cancer grading. As one example, both societies recommend that percentage Gleason pattern 4 is reported, but the exact way of reporting (eg, 3% of the core) is left to the individual pathologist by ISUP, while GUPS specifically recommends the use of increments of 5%, 10%, or every 10% afterward; obviously, the clinical relevance of this apparent contradiction is minimal. The recommendation to either assign a grade to intraductal carcinoma (IDC) if intermixed with invasive cancer (ISUP) or not (GUPS), is considered to be the most salient discordance between both societies. Two studies have shown that this leads to a modification of the global Grade Group in 12% to 23% of biopsies containing IDC, which might seem substantial.6,7 However, as IDCpositive cases represented 13% to 5% of all cancer biopsies in these series, respectively, this corresponded to an overall grade shift in <2%. Even if one does not assign a grade to IDC when intermixed with invasive Gleason score 3+3, most pathologists do believe these patients should not be considered to have the indolent disease, which further lessens the clinical impact.8 Despite the limited clinical impact of most of the discordances, the coexistence of 2 sets of recommendations may lead to confusion among pathologists and clinicians, or impair the generalizability of research data. From the clinicians’ point of view, the most urgent mandate for pathologists is to reduce our considerable interobserver variability in tumor grading, which now results in discordance rates of up to 20%. ISUP is currently engaged in this pursuit, which can exert a far greater impact on daily prostate cancer management than most of the reporting differences.