title: Independent surgical validation of the new prostate cancer grade-grouping system.
abstract: 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 (RP).
  
  
  METHODS
  Between 1994 and 2013, 3 694 consecutive men were treated with RP 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 modelling, and discriminatory comparison analyses. Separate analyses were performed based on biopsy and RP grade.
  
  
  RESULTS
  The 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 < 0.001). Similarly, the 5-year actuarial bRFS based on RP grade groups was 96.1%, 93.0%, 74.0%, 64.4%, and 49.9% for grade groups 1-5, respectively (P < 0.001). 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 < 0.001), and for RP grade groups were 2.09, 5.27, 5.86, and 10.42 (P < 0.001). The five-grade-group system had a higher prognostic discrimination compared with the commonly used three-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 for bRFS, and shown that the benefit is maintained after adjusting for important clinicopathological variables. The greater predictive accuracy of the new system will improve risk stratification in the clinical setting and aid in patient counselling.
authors.affiliation: Department of Radiation Oncology, University of Michigan, Ann Arbor, MI, USA. sprattda@med.umich.edu.
authors.forename: Daniel E
authors.identifier: http://orcid.org/0000-0002-5973-4741
authors.initials: DE
authors.lastname: Spratt
authors.affiliation: Department of Urology, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Adam I
authors.initials: AI
authors.lastname: Cole
authors.affiliation: Department of Urology, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Ganesh S
authors.initials: GS
authors.lastname: Palapattu
authors.affiliation: Department of Urology, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Alon Z
authors.initials: AZ
authors.lastname: Weizer
authors.affiliation: Department of Radiation Oncology, University of Michigan, Ann Arbor, MI, USA.
authors.forename: William C
authors.initials: WC
authors.lastname: Jackson
authors.affiliation: Department of Urology, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Jeffrey S
authors.initials: JS
authors.lastname: Montgomery
authors.affiliation: Department of Radiation Oncology, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Robert T
authors.initials: RT
authors.lastname: Dess
authors.affiliation: Department of Radiation Oncology, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Shuang G
authors.initials: SG
authors.lastname: Zhao
authors.affiliation: Department of Radiation Oncology, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Jae Y
authors.initials: JY
authors.lastname: Lee
authors.affiliation: Department of Urology, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Angela
authors.initials: A
authors.lastname: Wu
authors.affiliation: Department of Pathology, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Lakshmi P
authors.initials: LP
authors.lastname: Kunju
authors.affiliation: Department of Radiation Oncology, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Emily
authors.initials: E
authors.lastname: Talmich
authors.affiliation: Department of Urology, University of Michigan, Ann Arbor, MI, USA.
authors.forename: David C
authors.initials: DC
authors.lastname: Miller
authors.affiliation: Department of Urology, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Brent K
authors.initials: BK
authors.lastname: Hollenbeck
authors.affiliation: Department of Pathology, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Scott A
authors.initials: SA
authors.lastname: Tomlins
authors.affiliation: Department of Radiation Oncology, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Felix Y
authors.initials: FY
authors.lastname: Feng
authors.affiliation: Department of Pathology, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Rohit
authors.initials: R
authors.lastname: Mehra
authors.affiliation: Department of Urology, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Todd M
authors.initials: TM
authors.lastname: Morgan
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001706:Biopsy; D018572:Disease-Free Survival; D006801:Humans; D008297:Male; D008875:Middle Aged; D060787:Neoplasm Grading; D011468:Prostatectomy / Q000379:methods; D011471:Prostatic Neoplasms / Q000473:pathology* / Q000601:surgery*; D012189:Retrospective Studies
keywords: prostate cancer; prostate cancer grading; radical prostatectomy