Microscopic invasion of perivesical fat by urothelial carcinoma: implications for prognosis and pathology practice.

OBJECTIVE

To determine whether microscopic invasion of perivesical fat by urothelial carcinoma (stage pT3a) confers a different prognosis relative to deep muscle invasion (pT2b) and/or gross extravesical extension (pT3b) among patients with a given nodal status treated by cystectomy.

METHODS

Cancer records for patients diagnosed with stage pT2b-pT3b bladder cancer from 1998-2006 were obtained from the SEER database (n = 2388). Pathologic substage (pT3a vs pT2b vs pT3b) was the primary covariate of interest. Other covariates included age, sex, race, grade, number of nodes examined, number of positive nodes, nodal stages, and radiotherapy. Cox regression model was used to estimate the covariate-adjusted effect of tumor substages on all-cause mortality.

RESULTS

The risk of nodal metastases increased with increasing substage (pT2b = 20%, pT3a = 36%, pT3b = 48%, trend P <.001). Among patients with node-negative tumors, the adjusted hazard ratios for all-cause mortality were 1.68 (P <.001) for pT3a vs pT2b and 1.03 (P = .78) for pT3b vs pT3a tumors, whereas for node-positive disease, they were 1.42 (P = .009) for pT3a vs pT2b and 1.44 (P = .001) for pT3b vs pT3a tumors.

CONCLUSIONS

Microscopic invasion of perivesical fat was associated with significantly inferior survival relative to pT2b disease of the same nodal status. For node-positive pT3 tumors, more advanced pathologic substage (pT3b vs pT3a) was also associated with decreased survival. Our findings support the current practice of pathologic distinction between pT2b and pT3a disease and substaging of extravesical tumors based on microscopic versus gross extravesical extension.