Clinical and pathological significance of the level and extent of capsular invasion in clinical stage T1-2 prostate cancer
This study was performed to assess the relationship between the level and extent of prostatic capsular invasion (PCI) by cancer and the clinical and pathological features and prognosis of early-stage prostate cancer. We conducted a retrospective analysis of the clinical (age, stage, grade, prostate specific antigen [PSA] level) and pathological (tumor volume, stage, grade, surgical margins) features of 688 patients treated with radical prostatectomy to determine the pathological features and probability of recurrence associated with various levels of PCI. Radical prostatectomy specimens were serially sectioned and examined by whole-mount technique. Progression-free probabilities (PFP) after radical prostatectomy were determined by Kaplan-Meier and Cox proportional hazards regression analysis. Progression was defined as a rising serum PSA < or = 0.4 ng/mL or clinical evidence of recurrent cancer. Increasing clinical stage, Gleason grade in the biopsy specimen, and pretreatment serum PSA levels were each associated with increasing levels of PCI (P < .001). In the radical prostatectomy specimen, increasing levels of PCI were significantly associated with increasing tumor volume (P < .001), Gleason grade (P < .0001), seminal vesicle involvement (SVI, P < .001) and lymph node metastases (+LN, P < .001). None of 138 patients without capsular invasion had SVI or lymph node metastases (+LN), and all remained free of progression, even though some had large volume (up to 6.26 cm3) or poorly differentiated (Gleason sum up to 8) cancers. Invasion into the capsule (n = 271) was occasionally associated with SVI (6%) or +LN (3%) and a significantly (log-rank test) lower PFP of 87% at 5 years. Focal and extensive extraprostatic extension (EPE) were associated with progressively increased risk of SVI and +LN and lower PFP (73% and 42%, respectively). In a multivariate analysis, the level of PCI was an independent prognostic factor (P < .001). There is a strong association between the level of invasion of cancer into or through the prostatic capsule and the volume, grade, pathological stage, and rate of recurrence after radical prostatectomy. Prostate cancer does not appear to metastasize in the absence of invasion into the capsule regardless of the volume or grade of the intracapsular tumor. Subclassification of patients according to the levels of PCI provides valuable prognostic information.