Conditional prognostication of non-muscle invasive bladder cancer: a SEER-Medicare analysis
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Abstract
BACKGROUND: The risk of recurrence and progression is high among patients with non-muscle invasive bladder cancer (NMIBC). The challenge in disease management underlines the importance of accurate prognostic assessment. The risk profile of patients is expected to change at different follow-up times. Thereby, recurrence and progression rates during follow-up may differ from those estimated at diagnosis. Conditional survival, a prognostic measure that accounts for the time survived since diagnosis, provides a more accurate estimate than conventional survival estimated at time zero.
OBJECTIVE: To assess the 6-, 12-, 24-, 36-, and 60-month conditional recurrence-free survival (RFS) and progression-free survival (PFS) after index transurethral resection of bladder tumor (TURBT).
METHODS: The Surveillance, Epidemiology and End Results (SEER)-Medicare linked database was queried to identify patients aged ≥66-89 years diagnosed with Ta/Tis/T1 cN0 cM0 urothelial carcinoma of bladder (UCB) from 2000 to 2017. Conditional RFS and PFS estimates were estimated using the Kaplan-Meier method at pre-specified landmark times for the overall cohort and stratified by T stage and tumor grade. Univariable and multivariable Cox proportional hazards models were used to evaluate the associations of baseline characteristics with RFS and PFS at pre-specified landmark times.
RESULTS: The 60-month conditional RFS and PFS at baseline were 0.39 and 0.93 respectively. Given a 6, 12, 24, 36, 48, 60 months event-free survivorship, the 60-month RFS were 0.52, 0.63, 0.73, 0.78, 0.82, and 0.85 respectively; PFS were 0.94, 0.95, 0.96, 0.97, 0.97, and 0.97 respectively. Conditional RFS and PFS rapidly improved within the first 24 months and then plateaued. When stratified by T stage, patients with T1 tumors had significantly shorter RFS and PFS (p<0.01); however, the most notable survival gain with additional years survived was observed in this subgroup. On multivariable analyses, T stage at diagnosis was less predictive of RFS and PFS with longer landmark times, while tumor grade and female gender remained significant independent predictors of RFS and PFS.
CONCLUSION: The conditional survival analyses demonstrated improved survivorship with increased recurrence- and progression-free intervals. The risk of experiencing an event attenuated overtime with converging rates of survivorship across grade-stage subgroups. These data offer dynamic prognostication in directing more personalized care for patients with NMIBC.