Comparative assessment of the 1992 and 2002 pathologic T3 substages for the prediction of biochemical recurrence after radical prostatectomy

Abstract

Background: The objective of this study was to compare the ability of the 1992 American Joint Committee on Cancer (AJCC) TNM staging system for nonorgan-confined prostate carcinoma (PCa) (pathologic T3 [pT3a], pT3b,and pT3c) to predict biochemical recurrence (BCR) after radical prostatectomy with its revision from 1997/2002 (pT3a and pT3b).

Methods: The authors analyzed prospectively collected data from 971 consecutive patients with pT3 tumors who underwent radical prostatectomy alone at a single institution. According to the 1992 AJCC substages, 494 patients had pT3a PCa (51%), 85 patients had pT3b PCa (9%), 302 patients had pT3c PCa (31%) and 91 patients had pT3 PCa (9%) with metastatic lymph node invasion (LNI). Kaplan-Meier and Cox proportional hazards regression analyses were employed to assess the BCR rate using the preoperative prostate-specific antigen (PSA) level, surgical margin (SM) status, pathologic Gleason score, and LNI. The predictive accuracy of this "base" model was compared with models that added either the AJCC 1992 or the AJCC 1997/2002 staging definitions.

Results: BCR was observed in 345 patients (36%). The actuarial 5-year recurrence-free probability for patients with AJCC 1992 pT3a, pT3b, and pT3c PCa was 69%, 42%, and 33%, respectively, and differed significantly between men with pT3a tumors and men with pT3b tumors (log-rank test; P < 0.0005). In Cox regression analyses, the 1992 substages were associated significantly with BCR after controlling for PSA, SM status, Gleason grade, and LNI (P < 0.0005). The predictive accuracy of the base model (bootstrap-corrected concordance index, 0.739) was improved after addition of the 1992 TNM staging criteria (concordance index, 0.747). However, predictive accuracy was similar for the model that included the 1997/2002 substages (concordance index, 0.746).

Conclusions: Substaging of pT3 tumors according to the less complex 1997/2002 pT3 classification improved the predictive accuracy of the BCR rate virtually to the same extent as the more detailed 1992 classification. Therefore, the current data favor the use of the 1997/2002 pT3 substaging system.