Implementation of Grade Groups (GrGrs) has been widely accepted for reporting prostate cancer grade since the 2014 International Society of Urological Pathology consensus meeting. Despite their undisputed value for risk stratification, some GrGr are, a priori, quite heterogeneous in that they contain multiple Gleason patterns (GPs). In this regard, the prognostic significance of GP5 in biopsies with highest GrGr4 is uncertain and evaluated in this study. A search of all core biopsies positive for prostate cancer reviewed after 2005 was performed, and 71 cases with highest GrGr4 containing GP5 (i.e., 3 + 5 = 8 or 5 + 3 = 8; referred to as GrGr4/GP5pos) eligible for inclusion were identified. In addition, 95 core biopsy cases with highest GrGr4 and no GP5 (i.e, 4 + 4 = 8; referred to as GrGr4/GP5neg) were selected for comparison. Multiple pathologic parameters, including volume and amount of GP4, and clinical variables were collected to evaluate the influence of GP5 on disease recurrence, development of metastases, and disease-specific death. GrGr4/GP5pos cases did not show, as a group, statistically significant differences in prostatectomy findings, disease recurrence, metastases, and disease-specific mortality when compared with GrGr4/GP5neg cases. In addition, the risk of all outcomes evaluated in the study did not differ between the whole GrGr4/GP5pos and GrGr4/GP5neg groups. However, Kaplan-Meier analysis found that GrGr4/GP5pos cases with a significant amount of GP4 did show a higher risk of prostate cancer-specific death as well as bone and visceral metastases. Univariate Cox regression demonstrated that preoperative prostate specific antigen (PSA), total number of positive cores, and global GrGr5 were also associated with a higher chance of disease-specific death. In a multivariate model, only global GrGr5 and PSA >20 ng/dL remained statistically significant. This study suggests that the mere presence of GP5 in core biopsies with highest GrGr4 disease may not portend a worse prognosis. In these cases, accounting for the case-wide volume of GP4 by reporting a global GrGr appears to be more relevant as it identifies a subset of GrGr4/GP5pos patients with global GrGr5 who have a higher risk of metastases and prostate cancer-specific mortality.
Keywords: Biochemical; Cancer; Gleason; Grade group; PSA; Prostate.
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