Independent Surgical Validation of the New Prostate Cancer Grade Grouping System.

OBJECTIVE - To report the independent prognostic impact of the new prostate cancer grade grouping system in a large external validation cohort of patients treated with radical prostatectomy.

SUBJECTS/PATIENTS - Between 1994 and 2013, 3,694 consecutive men were treated by radical prostatectomy at a single institution.

To investigate the performance of and validate the grade-grouping system, biochemical recurrence-free survival (bRFS) rates were assessed using Kaplan Meier tests, Cox-regression modeling, and discriminatory comparison analyses. Separate analyses were performed based on biopsy and prostatectomy grade.

RESULTS - Median follow-up was 52.7 months. The 5-year actuarial bRFS for biopsy grade-groups 1-5 were 94.2%, 89.2%, 73.1%, 63.1%, and 54.7%, respectively (p<0.0001). Similarly, the 5-year actuarial bRFS based on surgical grade groups was 96.1%, 93.0%, 74.0%, 64.4%, and 49.9% for grade groups 1-5, respectively (p<0.0001). The adjusted hazard ratios for bRFS relative to biopsy grade group 1 were 1.98, 4.20, 5.57, and 9.32 for groups 2, 3, 4, and 5, respectively (p<0.0001), and for surgical grade groups were 2.09, 5.27, 5.86, and 10.42 (p<0.0001). The five-grade group system had a higher prognostic discrimination compared to the commonly used 3-tier system (Gleason score 6 vs 7 vs 8-10).

CONCLUSIONS - In an independent surgical cohort, we have validated the prognostic benefit of the new prostate cancer grade grouping system with respect to bRFS, and demonstrated that the benefit is maintained after adjusting for important clinicopathologic variables. The greater predictive accuracy of the new system will improve risk stratification in the clinical setting and aid in patient counseling. This article is protected by copyright. All rights reserved.

BJU international. 2016 Mar 24 [Epub ahead of print]

Daniel E Spratt, Adam I Cole, Ganesh S Palapattu, Alon Z Weizer, William C Jackson, Jeffrey S Montgomery, Robert Dess, Shuang G Zhao, Jae Y Lee, Angela Wu, Lakshmi P Kunju, Emily Talmich, David C Miller, Brent K Hollenbeck, Scott A Tomlins, Felix Y Feng, Rohit Mehra, Todd M Morgan

University of Michigan, Department of Radiation Oncology., Urology, University of Michigan, Ann Arbor, MI, 48109., Urology, University of Michigan, Ann Arbor, MI, 48109., Urology, University of Michigan, Ann Arbor, MI, 48109., University of Michigan, Department of Radiation Oncology., Urology, University of Michigan, Ann Arbor, MI, 48109., University of Michigan, Department of Radiation Oncology., University of Michigan, Department of Radiation Oncology., University of Michigan, Department of Radiation Oncology., Urology, University of Michigan, Ann Arbor, MI, 48109., Pathology, University of Michigan, Ann Arbor, MI, 48109., University of Michigan, Department of Radiation Oncology., Urology, University of Michigan, Ann Arbor, MI, 48109., Urology, University of Michigan, Ann Arbor, MI, 48109., Pathology, University of Michigan, Ann Arbor, MI, 48109., University of Michigan, Department of Radiation Oncology., Pathology, University of Michigan, Ann Arbor, MI, 48109., Urology, University of Michigan, Ann Arbor, MI, 48109.