Response to Neoadjuvant Chemotherapy and Survival in Micropapillary Urothelial Carcinoma: Data From a Tertiary Referral Center and the Surveillance, Epidemiology, and End Results (SEER) Program

We present our institutional experience with 46 patients diagnosed with micropapillary bladder carcinoma compared to conventional urothelial carcinoma, alongside data from Surveillance, Epidemiology, and End Results (SEER)-Medicare. We identified comparable pathologic response to neoadjuvant chemotherapy (NAC) across histologic subtypes, while micropapillary bladder carcinoma was not independently associated with worse outcomes, despite presenting with more aggressive features. The role of NAC should be further evaluated with additional studies in this setting. Background: Micropapillary urothelial carcinoma (MPC) is a rare urothelial carcinoma variant with conflicting data guiding clinical practice. In this study, we explored oncologic outcomes in relation to neoadjuvant chemotherapy (NAC) in a retrospective cohort of patients with MPC, alongside data from Surveillance, Epidemiology, and End Results (SEER)-Medicare. Patients and Methods: We retrospectively identified patients with MPC or conventional urothelial carcinoma (CUC) without any variant histology undergoing radical cystectomy (RC) in our institution (20032018). SEER-Medicare was also queried to identify patients diagnosed with MPC (2004-2015). Clinicopathologic data and treatment modalities were extracted. Overall survival (OS) was estimated with the Kaplan-Meier method. MannWhitney-Wilcoxon and chi-square tests were used for comparative analysis and Cox regression for identifying clinical covariates associated with OS. Results: Our institutional database yielded 46 patients with MPC and 457 with CUC. In SEER-Medicare, 183 patients with MPC were identified, and 63 (34%) underwent RC. In the institutional cohort, patients with MPC had significantly higher incidence of cN+ (17% vs. 8%), pN+ stage (30% vs. 17%), carcinoma-in situ (43% vs. 25%), and lymphovascular invasion (30% vs. 16%) at RC versus those with CUC (all P < .05). Pathologic complete response (ypT0N0) to NAC was 33% for MPC and 35% for CUC (P = .899). Median OS was lower for institutional MPC versus CUC in univariate analysis (43.6 vs. 105.3 months, P = .006); however, MPC was not independently associated with OS in the multivariate model. Median OS was 25 months in the SEER MPC cohort for patients undergoing RC, while NAC was not associated with improved OS in that group. Conclusion: Pathologic response to NAC was not significantly different between MPC and CUC, while MPC histology was not an independent predictor of OS. Further studies are needed to better understand biological mechanisms behind its aggressive features as well as the role of NAC in this histology variant.

Automated summary

The study found that the pathologic response to neoadjuvant chemotherapy was similar between micropapillary bladder carcinoma and conventional urothelial carcinoma. Although micropapillary bladder carcinoma presents with more aggressive features, it is not associated with worse outcomes compared to conventional urothelial carcinoma. Further research is needed to better understand the biological mechanisms behind the aggressive features of micropapillary bladder carcinoma and the role of neoadjuvant chemotherapy in this histological variant.