The validation of the 2014 International Society of Urological Pathology (ISUP) grading system for patients with high-risk prostate cancer: A single-center retrospective study.

Abstract

128 Background: Since the new 2014 grading system was recommended by the International Society of Urological Pathology (ISUP), it has been validated in patients with localized prostate cancer (PCa) and has shown excellent prognostic value. However, its predictive power in high-risk PCa remained unclear. Methods: Overall, 420 patients with high-risk PCa who underwent radical prostatectomy (RP) were included. Biochemical recurrence-free survival (BRFS) was set as the endpoint. Results: Biochemical recurrence occurred in 84/420 (20.0%) patients at the end of follow-up. Compared to the three-tier grouping system, the five-tier grouping system could more effectively distinguish the BRFS of patients with higher predictive accuracy (C-index: 0.599 vs 0.646). The BRFS of patients with grade group (GG) 1 and GG 2 was similar (p = 0.593). Also, the prognosis between those in the GG 2 and GG 3 could be clearly distinguished (p = 0.001). Whereas the discrimination capacity between patients with GG 3 and GG 4 was limited (p = 0.681). The high proportion of tertiary Gleason pattern 5 (TGP5) among patients with GG 3 might be an important confounder leading to the overlap of survival between GG 4 and GG 3. Conclusions: This study is the first one to validate the new 2014 ISUP grading system in patients with high-risk PCa who underwent RP. The 2014 system could effectively separate patients into five groups with high predictive accuracy. Notably, the existence of TGP5 needs to be routinely reported in clinical practice, which could help to support the predictive ability of the new grading system.