Impact of variant histology on disease-specific mortality and survival in patients with non-muscle invasive bladder cancer (NMIBC): A population-based analysis.

Abstract

332 Background: Prior studies have reported that variant histology is associated with poor outcomes in NMIBC. We utilized the Surveillance, Epidemiology and End Results (SEER) database to compare disease specific survival (DSS) and mortality (DSM) among the different variant histologies and urothelial carcinoma (UC). Methods: Patients diagnosed with NMIBC (Ta, Tis, T1) between 2004 and 2012 were eligible for analysis. Patients were separated into cohorts based on histology: UC and variant histology which included micro-papillary variant (MPV), neuroendocrine (NEC), squamous (SCC), adenocarcinoma (AC) and other variants (e.g., lymphoepithelial, giant cell, undifferentiated/anaplastic, sarcomatoid). Univariate and multivariable Cox proportional hazard analysis was used to evaluate the impact of variant histology on DSM after adjusting for other covariates. DSS was estimated amongst the different histologic and treatment groups using the Kaplan-Meier method and compared using Log-rank test. Results: We identified 111,756 patients, who were predominantly Caucasian (90%) and older than 70 years (57.5%; n=64,314). Variant histology accounted for 1.2% (n=1354) of cases. AC and SCC were the most common variant subtypes (26.4%; n=357 and 25.6%; n=347 respectively) followed by NEC (11.2%; n=151) and MPV (7.1%; n=96). On multivariable analysis adjusting for age, sex, race, T-stage, histologic grade and number of primary tumors, all variant subgroups except MPV were associated with increased DSM compared to UC (p<0.001). SCC had the worst 5-year DSS (53.8%; P<0.001) followed by NEC (65.1%) and AC (77.8%). Compared to treatment with TURBT or intravesical BCG, cystectomy was associated with improved DSS for variant histology patients with T1 tumors (75.8% vs. 66.3%; P<0.001). Conclusions: Variant histology, specifically SCC and NEC, was associated with significantly worse 5-year DSS in NMIBC. MPV, which is generally thought to be aggressive, had outcomes comparable to UC. Cystectomy was associated with improved DSS in patients with T1 disease and should be considered for NMIBC with variant histology.