Background: 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.
Methods: 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.
Results: 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.
Conclusions: 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.