Metastatic Tropism in Urothelial Carcinoma With Variant Histology: A Comprehensive NCDB Analysis

Introduction

Bladder cancer (BCa) with variant histology (VH) is notably aggressive and not as well studied as pure urothelial carcinoma (UC). The characteristics of variant BCa in the setting of metastatic disease may contribute to treatment response/resistance and subsequent disease progression. In this study, we sought to assess VH's impact on metastasis sites at presentation in metastatic BCa.

Methods

The National Cancer Database was queried from 2004 to 2019 to analyze cT1-4 cN0-3 cM1 patients with UC and VH BCa. The primary endpoint was the presence of metastasis to different organs. Binomial multivariable logistic regression was performed to determine the impact of VH on metastatic sites while controlling for multiple variables.

Results

Total 6005 eligible patients diagnosed with either UC or VH were included. Patients with small cell histology, the second most common VH, were more likely to have liver metastasis (OR: 4.335) while less likely to have lung metastases (OR: 0.521). Squamous cell carcinoma decreased the odds of bone metastasis (OR: 0.449). Adenocarcinoma increased the odds of lung metastases (OR: 1.690). Micropapillary VH is less likely to metastasize to the lungs (OR: 0.182) but more likely to spread to nonregional lymph nodes (OR: 2.623). Sarcomatoid subtype did not exhibit a statistically significant variation in the odds ratio for any of the metastatic sites.

Conclusion

This study comprehensively analyzes the limited research regarding metastatic BCa and VH. Our analysis underscores each subtype exhibiting heterogeneous metastatic tropism. Importantly, these findings illustrate the role of routine somatic gene expression profiling to guide adequate staging and treatment intensification and to offer a foundation for future studies of VH BCa care.