Prognostic significance of measured depth of invasion of urothelial carcinoma of the bladder compared to the 2010 American Joint Committee on Cancer pT2 and pT3 classifications.

PURPOSE: We compared the prognostic ability of the current American Joint Committee on Cancer (AJCC) staging system to direct measurement of the depth of tumor invasion into the muscularis propria and perivesical fat.
MATERIALS AND METHODS: We identified 148 patients with pT2N0 and 206 with pT3N0 who underwent radical cystectomy between 1990 and 2003. Clinicopathological features were reviewed. A measurement in mm was recorded of the depth of tumor invasion into the muscularis propria for pT2 cases and into perivesical fat for pT3 cases. Cancer specific survival between the pT2a and pT2b, and the pT3a and pT3b patient groups was estimated using the Kaplan-Meier method and compared with the log rank test. Optimal cutoff points for invasion depth in mm were estimated using an iterative estimation process to find the minimum p value with the maximum HR.
RESULTS: Of 148 patients with pT2 bladder cancer, including 76 with pT2a and 72 with pT2b, and 206 with pT3 bladder cancer, including 144 with pT3a and 62 with pT3b, there was no significant difference in cancer specific survival between the substages (p = 0.94 and 0.37, respectively). However, patients with measured invasion less than 4.5 mm into perivesical fat had significantly improved cancer specific survival compared to that in patients with invasion 4.5 mm or greater (5-year cancer specific survival 53% vs 40%, p = 0.02).
CONCLUSIONS: We found no significant difference in cancer specific survival when pT2 and pT3 tumors were stratified by AJCC substage. However, for pT3 tumors direct measurement of the depth of tumor invasion into perivesical fat identified a significant stratification of cancer specific survival at 4.5 mm.