Integrating Tertiary Gleason 5 Patterns into Quantitative Gleason Grading in Prostate Biopsies and Prostatectomy Specimens

Abstract

BackgroundPresence of small (tertiary) Gleason 5 pattern is linked to a higher risk of biochemical recurrence in prostate cancer. It is unclear, however, how to integrate small Gleason 5 elements into clinically relevant Gleason grade groups. ObjectiveTo analyze the prognostic impact of Gleason 5 patterns in prostate cancer and to develop a method for integrating tertiary Gleason 5 patterns into a quantitative Gleason grading system. Design, setting, and participantsProstatectomy specimens from 13 261 consecutive patients and of 3295 matched preoperative biopsies were available. Percentages of Gleason 3, 4, and 5 had been recorded for each cancer.Outcome measurements and statistical analysis: Results and limitationsOur data demonstrate that minimal Gleason 5 areas have strong prognostic impact in Gleason 7 carcinomas, while further expansion of the Gleason 5 pattern population has less impact. We thus defined an integrated quantitative Gleason score (IQ-Gleason) by adding a lump score of 10 to the percentage of unfavorable Gleason pattern (Gleason 4/5) if any Gleason 5 was present and by adding another 7.5 points in case of a Gleason 5 fraction >20%. There was a continuous increase of the risk of prostate-specific antigen recurrence with increasing IQ-Gleason. This was also true for subgroups with identical Cancer of the Prostate Risk Assessment Postsurgical scores (p<0.0001) or Gleason grade groups (p<0.0001). ConclusionsThe IQ-Gleason represents a simple and efficient approach for combining both quantitative Gleason grading and tertiary Gleason grades in one highly prognostic numerical variable. Patient summaryProstatectomy specimens (13 261) were analyzed to estimate the relevance of small Gleason 5 elements in prostate cancers. Even the smallest Gleason 5 areas markedly increased the risk of prostate-specific antigen recurrence after surgery. Larger fractions of Gleason 5 patterns had less further impact on prognosis. Based on this, a numerical Gleason score (integrated quantitative Gleason score) was defined by the percentages of Gleason 4 and 5 patterns, enabling a refined estimate of patient prognosis.