391 Background: Variant histology is increasingly recognized but its impact on outcomes is less well known compared to urothelial carcinoma (UC). We aim to evaluate the impact of variant histology on bladder cancer outcomes using the National Cancer Database (NCDB), a U.S. population-based cohort capturing approximately 70% of newly diagnosed cancer cases. Methods: We identified patients with bladder cancer from 2004 to 2013 treated with radical cystectomy. We compared clinical and pathologic characteristics between those with UC and those with variant histology. Chi-square test was utilized for categorical variables and Independent Samples t-test for continuous variables. Multivariable Cox regression was used with hazard ratios (HR) and 95% confidence intervals (CI) to identify independent predictors of overall survival. Results: A total of 40,918 patients were identified with mean age 67 years, with male (75%) and Caucasian (90.9%) predominance. Median follow-up was 36.9 months (IQR 16.1-67.5). Squamous cell carcinoma (4.4%), small cell carcinoma (1.6%) and micropapillary (0.9%) were the most common variant histologies. Variant histology was found more commonly in women (35.6% vs 23.4%, p < 0.05), black (8.8% vs 5.6%, p < 0.05), stage pT3 or T4 (67% vs 50.2%, p < 0.05) and node positive (30.8% vs 26.9%, p < 0.05). In adjusted models squamous cell carcinoma (HR 1.3, 95% CI 1.2-1.4), small cell carcinoma (HR 1.6, 95% CI 1.5-1.8) and black ethnicity (HR 1.2, 95% CI 1.1-1.2) were independent predictors of increased mortality risk while micropapillary was associated with decreased risk (HR 0.8, 95% CI 0.7-1.0) after controlling for age, gender, surgical margin status, pathologic T stage, pathologic N stage and history of chemotherapy. All associations remained statistically significant (p < 0.05). Conclusions: Non-urothelial histology was associated with worse overall survival in patients with bladder cancer treated with radical cystectomy; however, contrary to some previous reports, micropapillary variant was associated with lower risk of death. In addition, black ethnicity was associated with worse survival. Further investigation is needed to explore the impact of variant histology as well as other socioeconomic factors on survival after cystectomy.
Adjuvant chemotherapy is ineffective in patients with bladder cancer and variant histology treated with radical cystectomy
