Grade Groups Provides Improved Predictions of Pathologic and Early Oncologic Outcomes Compared with Gleason Score Risk Groups

Abstract

PurposeThe grade grouping (GG) system was introduced in 2013. Data from academic centers suggests GG better distinguishes between prostate cancer risk groups than the Gleason score (GS) risk groups. We compared the performance of both for predicting pathological/recurrence outcomes using data from Michigan Urological Surgery Improvement Collaborative (MUSIC). Materials and MethodsPatients undergoing biopsy and radical prostatectomy (RP) within MUSIC (3/2012-6/2017) were classified according to GG and GS. Outcomes included presence/absence of extraprostatic extension (EPE), seminal vesical invasion (SVI), positive lymph nodes (N1), positive surgical margins (PSM), and time to cancer recurrence (defined by having post-operative PSA≥0.2). Logistic and cox regression models were used to compare the difference in outcomes. Results8052 patients were identified. Controlling for patient characteristics, significantly higher risks of EPE, SVI, and N1 were observed for biopsy GG3 vs. GG2, and for GG5 vs. GG4 (p<0.001). Biopsy GG3, GG4, and GG5 also had shorter time to biochemical recurrence (BCR) when compared to GG2, GG3, and GG4, respectively (p<0.001). GG3, GG4, and GG5 at RP were each associated with greater probability of recurrence compared to the next lower GG (p<0.001). GG (vs. GS) had better predictive power for EPE, SVI , N1, and BCR. ConclusionsGG at biopsy and RP allows for better discrimination of recurrence-free survival between individual risk groups than GS risk groups with GG2, GG3, GG4, and GG5 each incrementally associated with increased risk.