Depth of Invasion of Urinary Bladder Cancer: Comparison of Direct Measurement Versus 2010 American Joint Committee on Cancer (AJCC) pT2 and 3 Classification
Shabnam Zarei, Igor Frank, Stephen A Boorjian, Simon Kim, Chris J Weight, Robert Tarrell, Prabin Thapa, John C Cheville. Mayo Clinic, Rochester, MN
Background: The clinical significance of sub-staging muscle invasive (AJCC pT2a and pT2b) and perivesical fat invasive (AJCC pT3a and pT3b) urinary bladder cancer remains uncertain. The objective of this study was to compare the cancer-specific (CS) outcome of pT2 and pT3 sub-staging and to compare the current AJCC staging system to a direct measurement of depth of invasion into muscularis propria and into perivesical fat.
Design: A search of the Mayo Clinic Cystectomy Registry identified 105 pT2N0 and 144 pT3N0 patients that underwent radical cystectomy or cystoprostatectomy between 1993 and 2003. The clinical and pathologic features of the cases were reviewed, and a measurement in millimeters (mm) of the depth of invasion into muscularis propria (for pT2 patients) and depth of invasion into perivesical fat (for pT3 patients) was recorded. Cancer-specific survival rates among pT2a/b and pT3a/b patient groups and depth of invasion (mm) were compared using the Kaplan-Meier method and Log rank test. Optimal cut-points for depth of invasion (in mm) were estimated using an interactive estimation process of finding the minimum p value with the maximum Hazard ratio.
Results: Of 105 of patients with pT2 bladder cancer (51 pT2a and 54 pT2b), there was no significant difference in CS outcome between pT2a and pT2b and no optimal cutpoint in mm that identified a difference in survival (p=0.6). Of 144 patients with pT3 bladder cancer (99 pT3a and 45 pT3b), there was no significant difference in CS survival (p=0.4). However, patients with invasion less than 3.5 mm into perivesical fat had a significantly improved CS survival compared to patients with invasion 3.5 mm and greater (CS survival at 5-yrs, 51% versus 33%, respectively; p<0.03). Finally, there was a significant difference in CS outcome between patients with overall classification of pT2 versus pT3 tumors (CS survival at 5-yrs, 68% vs. 42%, respectively; p<0.0002).
Conclusions: There is no significant difference in CS survival when pT2 and pT3 tumors were stratified according to the AJCC sub-staging. However, for pT3 tumors, the direct measurement of depth of invasion into perivesical fat identified a significantly different CS survival difference at 3.5 mm. Therefore, pT2a/b should be consolidated into a single pT2 classification while the separation of pT3 into a and b should be based on a direct measurement of the depth of perivesical fat invasion.
Category: Genitourinary (including renal tumors)
Monday, March 19, 2012 1:15 PM
Platform Session: Section A, Monday Afternoon