Another set of data validate the proposed new prostate cancer grading system

Another independent study has validated the proposed new prostate cancer grading system developed by members of the International Society of Urologic Pathologists (ISUP) and discussed previously on this web site.

In a new paper by Spratt et al. in BJU International, the authors write that:

In an independent surgical cohort, we have validated the prognostic benefit of the new prostate cancer grade grouping system with respect to [biochemical recurrence-free survival], 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.

Spratt et al. looked at data from a series of 3,694 consecutive prostate cancer patients, all treated by radical prostatectomy at a single institution from 1994 through 2013. In order to assess the predictive accuracy and validate the new grade-grouping system, they assessed the patient’s projected biochemical recurrence-free survival (bRFS) rates using Kaplan-Meier tests, Cox regression modeling, and discriminatory comparison analyses. They also conducted two separate sets of analyses using grading data from the biopsy specimens and the prostatectomy specimens from all the patients.

The authors report the following:

  • Average (median) patient follow-up was 52.7 months.
  • The 5-year actuarial bRFS rates based on biopsy specimens were
    • 94.2 percent for grade-group 1
    • 89.2 percent for grade-group 2
    • 73.1 percent for grade-group 3
    • 63.1 percent for grade group 4
    • 54.7 percent for grade-group 5
  • The 5-year actuarial bPFS rates based on post-surgical prostatectomy specimens were
    • 96.1 percent for grade-group 1
    • 93.0 percent for grade-group 2
    • 74.0 percent for grade-group 3
    • 64.4 percent for grade-group 4
    • 49.9 percent for grade-group 5
  • The adjusted hazard ratios (aHRs) for biochemical recurrence compared to grade-group 1, based on biopsy specimens, were
    • 1.98 for grade-group 2
    • 4.20 for grade-group 3
    • 5.57 for grade-group 4
    • 9.32 for grade-group 5
  • The aHRs for biochemical recurrence compared to grade-group 1, based on prostatectomy specimens, were
    • 2.09 for grade-group 2
    • 5.27 for grade-group 3
    • 5.86 for grade-group 4
    • 10.42 for grade-group 5
  • The five-grade group system had a higher prognostic discrimination compared to the commonly used three-tier system using Gleason scores of 6 vs. 7 vs. 8-10.

This is at least the fourth independent study to confirm the predictive accuracy of the proposed new grading system and to argue that it will offer more accuracy and simplify patient counseling … although The “New” Prostate Cancer InfoLink understand that there are plenty of patient advocates (and clinicians) who do not buy into this argument.

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