The Clinical Significance of pT3a Lesions as Well as Unilateral Versus Bilateral Invasion Into the Seminal Vesicle in Men With pT3b Prostate Cancer: A Proposal for a New pT3b Subclassification

Abstract

Context.— Seminal vesicle invasion (SVI) as pT3b prostate cancer generally, but not uniformly, indicates poor prognosis. Objective.— To determine the clinical impact of pT3a lesions (ie, extraprostatic extension other than seminal vesicle or bladder invasion [EPE], microscopic bladder neck invasion [mBNI]), as well as unilateral (Uni) versus bilateral (Bil) SVI in pT3b disease. Design.— We assessed radical prostatectomy findings and long-term oncologic outcomes in 248 consecutive patients with pT3b disease. Results.— Focal EPE, nonfocal EPE, mBNI, Uni-SVI, and Bil-SVI were identified in 13 (5.2%), 206 (83.1%), 48 (19.4%), 109 (44.0%), and 139 (56.0%) cases, respectively. Of possible combinations, we eventually divided our cases into 3 cohorts—Group 1: Uni/Bil-SVI and EPE−/mBNI− (n = 28; 11.3%); Group 2: Uni-SVI and EPE or mBNI (n = 103; 41.5%); and Group 3: Bil-SVI and EPE or mBNI (n = 70; 28.2%) or Uni/Bil-SVI and EPE+/mBNI+ (n = 47; 19.0%). Group 3 patients showed significant adverse histopathologic findings, compared with Group 1 or Group 2 patients. Kaplan-Meier analysis revealed that the prognosis was worse in the following order: Group 1, Group 2, and Group 3; and the differences in progression-free survival between any 2 groups were statistically significant. These significant differences were also seen in subgroups, such as those without or with adjuvant therapy before recurrence and those without lymph node metastasis. Additionally, Group 3 patients had a significantly higher risk of cancer-specific mortality than Group 2 patients. In multivariate analysis (Group 2 as a reference), Group 1 (hazard ratio [HR] = 0.169, P = .01) and Group 3 (HR = 1.620, P = .04) showed significance for progression. Conclusions.— From these significant findings, we propose a novel pT3b subclassification, namely pT3b1 (Group 1), pT3b2 (Group 2), and pT3b3 (Group 3), which more accurately stratifies its prognosis.