Bladder Cancer: A Comparison Between Non-urothelial Variant Histology and Urothelial Carcinoma Across All Stages and Treatment Modalities.

Abstract

The purpose of this study was to evaluate stage at presentation, treatment rates, and cancer-specific mortality (CSM) of non-urothelial variant histology (VH) bladder cancer (BCa) relative to urothelial carcinoma of the urinary bladder (UCUB). Within the Surveillance, Epidemiology, and End Results registry (SEER, 2004-2016), patients with VH BCa and UCUB were identified. Stage at presentation and treatment rates, as well as multivariably adjusted and matched CSM rates according to TNM stage within each histologic subtype, were reported. Of all 222,435 eligible patients with BCa, 11,147 (5.0%) harbored VH. Among those, squamous cell carcinoma accounted for 3666 (1.6%) patients, adenocarcinoma for 1862 (0.8%), neuroendocrine carcinoma for 1857 (0.8%), and other VH BCa for 3762 (1.7%) of the study cohort. Patients with VH BCa showed invariably more advanced TNM stage at presentation compared with patients with UCUB. Treatment rates according to TNM stages showed similar distribution of cystectomy rates in VH BCa and UCUB. However, important differences in the distribution of radiotherapy and chemotherapy rates existed within VH BCa and in comparison with UCUB. Furthermore, even after multivariable adjustment and matching with UCUB, squamous cell carcinoma exhibited higher CSM (hazard ratios, 1.43-1.95; all P< .01) across all stages. All other VH predominantly exhibited higher CSM than UCUB in either non-muscle-invasive or muscle-invasive nonmetastatic stages. TNM stage at diagnosis is invariably more advanced in all patients with VH BCa versus patients with UCUB. Of all VH BCa, in multivariably adjusted stage for stage analyses, squamous cell carcinoma appears to have the worst natural history. All other VH subgroups exhibited more aggressive natural history than UCUB in nonmetastatic stages only.