Micropapillary Bladder Cancer: Insights from the National Cancer Database

Introduction: Micropapillary bladder cancer (MPBC) is a variant histology of urothelial carcinoma (UC) that is associated with poor outcomes however given its rarity, little is known outside of institutional reports. We sought to use a population-level cancer database to assess survival outcomes in patients treated with surgery, radiation therapy and/or chemotherapy. Materials and Methods: The National Cancer Database (NCDB) was queried for all cases of MPBC and UC using International Classification of Disease-O-3 morphologic codes between 2004-2014. Primary outcome was survival outcomes stratified by treatment modality. Treatments included radical cystectomy (RC) with or without neoadjuvant chemotherapy (NAC) or adjuvant chemotherapy (AC). Results: Overall 869 patients with MPBC and 389,603 patients with UC met the inclusion criteria. Median age of the MPBC cohort was 69.9 years (58.9-80.9) with the majority of the cohort presenting with high-grade (89.3%) and muscle invasive or locally advanced disease (47.6%). For cT1 MPBC, outcomes of RC and BPS were not statistically different. For≥cT2 disease, NAC showed a survival benefit compared with RC alone for UC but not for MPBC. On multivariable analysis, MPBC histology independently predicted worse increased risk of death. On subanalysis of the MPBC RC patients, NAC did not improve survival outcomes compared with RC alone. Conclusions: Neoadjuvant chemotherapy utilization and early cystectomy did not show a survival benefit in patients with MPBC. This histology independently predicts decreased survival and prognosis is poor regardless of treatment modality. Further research should focus on developing better treatment options for this rare disease.