Modification of the pT2 substage classification in prostate adenocarcinoma

The current substage classification of pT2 prostate cancer (AJCC, 7th edition, 2010) into pT2a (unilateral tumors <1/2 of lobe), pT2b (unilateral tumors ≥1/2 of lobe), and pT2c (bilateral tumors) is of questionable relevance. Many studies show no difference in prognosis between substages, and incidence of pT2b prostate cancer is low. Other classification systems have been proposed based on tumor volume, as measured by dominant nodule size or tumor percentage. We characterized pT2b tumors and assessed the utility of current pT2 substaging in predicting biochemical recurrence-free survival after radical prostatectomy and compared them with different substaging methods based on tumor volume. Patients with pT2 tumors were selected among patients who underwent radical prostatectomy from 1998 to 2008. Dominant nodule size was dichotomized as <1.6 cm versus ≥1.6 cm. Tumor percentage was dichotomized as ≤25% versus >25%. Kaplan-Meier analysis and multivariate Cox proportional hazard regression models were used to evaluate pathological parameters predictive of biochemical recurrence-free survival. Of 785 patients who met criteria, 145 (18.5%) were pT2a, 15 (1.9%) were pT2b, and 625 (79.6%) were pT2c. The pT2 substages were not significant predictors of biochemical recurrence-free survival on univariate or multivariate analysis. In a multivariate model, tumor percentage >25% (P=.002) was associated with decreased biochemical recurrence-free survival. In patients with stage pT2 prostate cancer, the current substaging method lacks predictive value for biochemical recurrence-free survival after accounting for other pathologic and clinical predictors. However, tumor percentage (≤25% versus >25%) is a promising approach to substaging of pT2 prostate cancer based on its prognostic significance.