1762P MERINOS: Metastatic non muscle invasive urothelial carcinoma - An observational study

Common evolution of non-muscle invasive bladder cancer (NMIBC) is local recurrence or progression to muscle invasive bladder cancer (MIBC). Metastatic disease usually occurs only after progression to muscle invasive disease. However, some patients (pts) with NMIBC might develop metastases without progression to MIBC (mNMIBC). Yet, characteristics and clinical evolution of this atypical presentation of bladder cancer are unknown. In this retrospective, multicentric French study, we aimed to describe clinical characteristics of mNMIBC (synchronous or metachronous). Pts with a history of MIBC (proven or suspected, histologically or radiologically), upper tract urothelial carcinoma or intra-diverticular bladder tumour were excluded. Survival was assessed using Kaplan Meier and Cox regression model. From 2005 to 2021, 70 pts were included from 17 French hospitals. Patients were mostly men (83%); median age at diagnosis for NMIBC was 63,8 years. The majority (93% of pts) had a high or very high risk NMIBC. Overall, 63% received intravesical BCG instillations and 21% of them were BCG-unresponsive; 24% of the cohort had a cystectomy. 19% of the pts had an upfront mNMIBC whereas 81% had metachronous mNMIBC. The median time to metastatic progression was 22.2 months [19,8; 54 months]. 21% of pts had lymph nodes only metastatic disease. The median overall survival from metastatic diagnosis was 27 months [16,6; NR]. The first line treatment was platinum-based chemotherapy for 84% of pts (cisplatin for 44%, and carboplatin for 40%). The objective response rate was 67%(standard deviation 0.32) (CR: 43% – PR: 24%) and the median time to treatment failure was 12.5 months [8,3; 14,7]. This study highlights that NMIBC can evolve to metastatic disease (upfront or metachronous presentation) without proven progression to MIBC. Objective response to platinum-based chemotherapy in the present mNMIBC cohort compared favourably with historical data in pts with metastatic urothelial carcinoma. A molecular profiling is ongoing to better understand the oncogenesis of this aggressive subtype of NMIBC.