Comparing radical cystectomy with trimodal therapy for patients diagnosed with bladder cancer: Critical assessment of statistical methodology and interpretation of observational data.

373Background: Treatment guidelines for muscle-invasive bladder cancer recommend radical cystectomy. However, use of trimodal therapy has increased in recent years with conflicting survival outcomes. The aim of this study was to compare radical cystectomy and trimodal therapy in terms of survival outcomes and cost of treatment according to varying statistical methodology in order to interpret findings using observational data. Methods: Patients aged 66 years or older diagnosed with clinical stage T2-4a bladder cancer from January 1, 2002-December 31, 2011 were included from the Surveillance, Epidemiology, and End Results (SEER)-Medicare database. Outcomes included cancer-specific survival, overall survival, and 6-month costs. Cox proportional hazards regression, propensity score matching (PSM) and inverse probability of treatment weighting (IPTW) were used to control for baseline differences between patients undergoing radical cystectomy vs. trimodal therapy, and to determine predictors for overall and ca...