Conditional survival after radical cystectomy for non-metastatic muscle-invasive squamous cell carcinoma of the urinary bladder: a population-based analysis

Abstract

Purpose: To assess the effect of event-free survival duration on cancer-specific mortality (CSM) after radical cystectomy (RC) in nonmetastatic muscle-invasive squamous cell carcinoma of the urinary bladder. Methods: RC patients treated for non-metastatic muscle-invasive squamous cell carcinoma of the urinary bladder were identified within the Surveillance, Epidemiology, and End Results database (2000-2018). Independent predictor status for CSM of T and N stage groupings (i.e., T2N0, T3N0, T4N0, and TanyN1-3) was tested in multivariable Cox-regression models. Conditional 5-year CSM-free estimates were assessed at baseline and at 4 specific event-free survival times (i.e. 6, 12, 18 and 24 months), within each of the 4 examined stage groups. Results: Of 981 RC patients, 206 (21%), 416 (42%), 152 (16%), and 207 (21%) were T2N0, T3N0, T4N0, and TanyN1-3, respectively. In multivariable Cox-regression models T3N0 (HR 1.94), T4N0 (HR 5.22), and TanyN1-3 (HR 6.62) were independent predictors of CSM, relative to T2N0. In conditional survival analyses based on 24 months event-free status, survival estimates were: 89% for T2N0 vs. 76% at baseline (Delta = 13%), 84% for T3N0 vs. 58% at baseline (Delta = 26%), 69% for T4N0 vs. 25% at baseline (Delta = 44%), 69% for TanyN1-3 vs. 22% at baseline (Delta = 47%). Conclusions: Event-free status at 24 months of follow-up is associated with substantially higher CSM-free survival than when CSM-free survival is predicted at baseline. The magnitude of this effect is most pronounced in TanyN1-3 and T4N0 patients, intermediate in T3N0 and more modest, nonetheless important, in T2N0.