Optimizing treatment approaches in nested bladder tumors: A multicenter retrospective study.

743 Background: Identifying optimal treatment strategies in nested bladder tumors is critical. This multicenter study aims at evaluating progression-free survival (PFS) end overall survival (OS) according to disease extent, presentation and treatment including Bacillus Calmette-Guérin (BCG), radical cystectomy (RC) and chemotherapy (CT). Methods: Data were collected from 61 patients with nested bladder tumors across 5 centers over a 10-year period (2013–2023). Patients were stratified according to 1) time of diagnosis of nested variant (disease onset Vs recurrence) 2) disease extent (NMIBC vs MIB, vs cN+ Vs M+) 3) treatment groups based on their initial treatment: ( BCG ± RC vs RC only Vs RC + CT). Kaplan-Meier analysis was used to assess median PFS (mPFS) and median OS (mOS), while p-values <0.05 was used to determine statistical significance across groups. Results: The median follow-up was 30.6 months (95% CI: 16.4–40.6). At diagnosis 15 (24.6%) were NMIBC, 26 (42.6%) MIBC, 15 (24.6%) N+ and 5 (8.2%) metastatic (M). Of the 15 NMIBC 80% received initial BCG. Pts with nested bladder tumors at onset had worse PFS and OS (mPFS of 99.6 months (95% CI: 55.2-NR) and mOS of 107.3 months (95% CI: 71.6-NR) than those with nested bladder tumor at recurrence mPFS of NR (95% CI: 42.1-NR) and mOS 138.4 (95% CI: 51.7-NR). None of these differences were statistically significant. Patients with M and N+ stages showed a trend towards a worse prognosis than those with NMIBC and MIBC, with no statistically difference in mPFS and mOS between MIBC and NMIBC stages. According to treatment, the best mPFS and mOS were recorded among patients receiving RC and CT [mPFS 99.6 months (95% CI: 55.2-NR) and mOS of 107.3 months (95% CI: 107.3-NR)]. Those receiving BCG followed by RC group had a mPFS of 84.2 months (95% CI: 68.1-NR) and mOS of 85.9 months (95% CI: 71.6-NR) while those undergoing RC alone apparently had the worse mPFS of 42.1 months (95% CI: 42.1-NR) and mOS of 51.7 months (95% CI: 14.7.1-NR). None of these differences were statistically significant. Conclusions: This study represents the largest case series of nested bladder tumors. It suggests limited benefit from BCG treatment. Most patients had advance disease, most of NMIBC finally need CT. Diagnosis at recurrence and combination of RC and CT tend to better survivals. Analyses that are more detailed are ongoing to evaluate clinical benefits according to the different clinical features.