The prognostic role of tertiary Gleason pattern 5 in a contemporary grading system for prostate cancer

Recently, a new prostate cancer (PC) grading system has been introduced, where Gleason score (GS) 7 (3+4) and GS 7 (4+3) are categorized into two separate groups. However, GS 7 with tertiary Gleason pattern 5 (TGP5) was not incorporated in the new grading system. In the present study, we validated the prognostic role of TGP5 in the new classification.

We retrospectively reviewed the records of 1396 patients with localized GS 6-8 PC (pT2-3N0M0) who underwent radical prostatectomy at our institution between 2005 and 2014. After excluding patients who received neoadjuvant or adjuvant therapy, or had incomplete pathological or follow-up data, 1229 patients were included in the final analysis. The Kaplan-Meier method was used to estimate and compare the probabilities of biochemical recurrence (BCR). Cox regression models were used to investigate associations between variables and the risk of BCR.

Of 732 GS 7 patients, 75 (10.2%) had a TGP5. The BCR-free survival rate for men with TGP5 was significantly worse than for those without TGP5 (P<0.001). In multivariate Cox regression analyses for GS 7 PC, TGP5 was a significant predictor of BCR (hazard ratio 1.750, P=0.027). When the total cohort was stratified into four grade groups according to the new classification, group 2 with TGP5 had a BCR risk comparable to group 3, and group 3 with TGP5 behaved like group 4.

Our study shows that TGP5 increased the BCR risk after RP in GS 7 PC. Moreover, we demonstrated that the presence of a TGP5 in GS 7 upgraded the BCR risk to one comparable with the next higher category under the new classification. These findings support incorporating TGP5 into GS 7 to aid with future risk assessment and follow-up scheduling for PC.