The Natural History, Treatment Pattern, and Outcomes of Patients With Micropapillary Bladder Carcinoma.

Objective: Micropapillary bladder carcinoma (MPBC) is a rare variant of urothelial cancer. Most literature on MPBC is from case series reports. This study's objective was to examine the epidemiology, natural history, and prognostic factors of MPBC using a population-based registry, in addition to a literature review.

Methods: The Surveillance, Epidemiology, and End Results (SEER) database identified 98 histologically confirmed MPBC patients from 2001 and 2007. In addition, 213 MPBC cases were identified in published literature. The clinical, demographic characteristics, treatment, and survival outcomes were compared between these 2 cohorts.

Results: Among patients identified in SEER, MPBC accounted for approximately 0.01% of primary bladder tumors, with the median age of 72 years (range, 26 to 95 y). Among the MPBC cases, 56.1% had muscle invasive disease, 75.5% had poor or undifferentiated histology, and 30.6% underwent a radical or partial cystectomy. The 1-, 3-, and 5-year overall survival rates for the SEER cohort were estimated at 84.5%, 57.3%, and 42.3%, respectively. Using multivariate analysis, tumor stage and marital status were the most significant predictors for cancer-specific survival. When comparing published single-institution studies to the SEER cohort, significant differences existed in demographic characteristics including age at diagnosis, male-to-female ratio, tumor stage, cystectomy treatment, and survival outcomes, likely reflecting differences in practice patterns.

Conclusions: This is the first population-based study to analyze MPBC's epidemiology, tumor characteristics, and survival rates. Emphases on early detection, cystectomy, and multimodality in treatment are needed.