Analysis of clinical stage T2 prostate cancer: do current subclassifications represent an improvement?

Abstract

The purpose of this study was to determine whether the extent of palpable cancer within the prostate predicts outcome after radical prostatectomy. We combined prospectively collected data on 1,755 consecutive clinical stage T2 patients treated with radical prostatectomy alone at four institutions. According to the 1992 American Joint Committee on Cancer tumor-node-metastasis system, 645 (37%) were T2a, 758 (43%) were T2b, and 352 (20%) were T2c. Kaplan-Meier and proportional hazards regression analyses were performed on the 1992 and 1997 T2 subclassifications. After controlling for the effects of prostate-specific antigen (PSA) and biopsy Gleason sum, the two staging systems were compared for their ability to predict recurrence-free survival (RFS). Adjusted RFS curves were constructed using the corrected group prognosis method. Follow-up ranged from 1 to 166 months (median, 26 months). Cancer recurred in 417 (24%) of the T2 patients. The 1992 (P =.005) but not the 1997 (P =.100) T2 subclassification predicted outcome after controlling for PSA and Gleason sum. After covariate adjustment, RFS was 7% higher at 5 years in the 1992 T2a subcategory relative to the T2b subcategory. The 1992 American Joint Committee on Cancer system is superior to the 1997 system, and the former adds prognostic information to a model containing pretreatment PSA and Gleason sum. These results suggest that 1992 T2 subclassification derived from palpable findings improves prognostication over the 1997 subclassification.