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Introduction:
We evaluated the clinical and prognostic impact of bladder cancer histologic variants using a large population-based database.
Materials & Methods:
Using the Surveillance, Epidemiology, and End Results database (SEER), we identified bladder cancer patients from 2001-2011, and categorized them according to histologic differentiation. Disease-specific survival (DSS) was calculated using the Kaplan-Meier method. Cox proportional hazards regression model was used to predict association with disease-specific mortality (DSM). In addition, we fitted multivariate logistic regression models to predict the impact of histologic variants on muscle-invasion (MI), nodal involvement (NI), and metastatic disease (MD).
Results:
The cohort included 160885 urothelial (96.5%) and 5781 variants (3.5%). The latter were divided into: 2205 squamous, 1526 adenocarcinoma, 799 small cell, 462 spindle cell, 279 neuroendocrine, 270 signet-ring cell, and 240 micropapillary bladder tumors. Urothelial cancers overall had the best median DSS. Of the non-urothelial variants, micropapillary and squamous had the best and worst DSS respectively (p<0.001). On multivariable analysis predicting DSM, micropapillary and squamous variants had the best and worst prognosis respectively (HR 0.7, p=0.049 and HR 2.85, p<0.001), compared to urothelial tumors. On multivariable analysis predicting MI, NI, and MD: squamous (OR 22.42, p<0.001), signet-ring cell (OR 3.2, p<0.001), and adenocarcinoma (OR 5.15, p<0.001) had poorer prognosis respectively, compared to urothelial tumors.
Conclusions:
Despite accounting for a minority of bladder cancers, non-urothelial variants are associated with worse outcomes. It is essential to recognize the potential implications of these variants when deciding treatment.