Does Subclassification of Pathologically Organ Confined (pT2) Prostate Cancer Provide Prognostic Discrimination of Outcomes after Radical Prostatectomy?

Abstract

We tested the latest update in the prostate cancer staging system by assessing the prognostic association of pT2 subclassification with the probability of survival related outcomes in patients who underwent radical prostatectomy. We retrospectively analyzed the records of a total of 15,305 patients who underwent radical prostatectomy at 2 referral centers between 1985 and 2016, and had pT2 disease at the final pathological evaluation. Descriptive statistics were used to compare baseline data stratified by pT2 substages (pT2a/b vs pT2c). Cox regression models were adjusted for institution analyzed differences in the rate of biochemical recurrence, metastasis, cancer specific death and overall mortality. Multivariable Cox regression models were used to evaluate the predictive value of pT2 subclassification for survival, including the linear predictor from the Stephenson nomogram. Prostate specific antigen levels and Gleason score differed significantly between the pT2 substages (each p <0.0001). At a median followup of 6.0 years (IQR 3.3–10.1) 2,083 patients had biochemical recurrence, 161 had metastases, 43 had died of prostate cancer and 1,032 had died of another cause. On univariate analysis the pT2 subclassification was significantly associated with biochemical recurrence (p = 0.001) and distant metastasis (p = 0.033) but not with cancer specific death (p = 0.6) or overall mortality (p = 0.3). Multivariable analysis showed no evidence of a significant association between the pT2 subclassification and biochemical recurrence (p = 0.4) or distant metastasis (p = 0.6). Multivariable analysis of cancer specific death and overall mortality was omitted due to lack of significance on univariate analysis. Subclassification of pT2 prostate cancer is not a prognostic indicator of survival related outcomes after radical prostatectomy. Our results validate the elimination of pT2 substages in the updated staging system.