Real world outcome of neuroendocrine carcinomas of the bladder compared to conventional tumors of the bladder.

Abstract

e16591 Background: Platinum based neoadjuvant chemotherapy (NAC) has been shown to be a beneficial treatment strategy that increases overall survival (OS) in bladder cancer (BC) when compared to radical cystectomy (RC) alone, and the benefit was observed in multiple histologies associated with BC. Neuroendocrine carcinomas (NEC) of the bladder are a rare and aggressive BC subtype known to be chemotherapy sensitive, with improvement in oncological outcomes after NAC. However, due to inherent differences in natural progression of different BC histologies, higher chemosensitivity does not necessarily mean NEC has better outcomes compared to other BC histologies after NAC. We analyzed the outcomes of NEC patients and non-NEC BC patients to investigate the differences in benefit observed from NAC, and in oncological outcomes. Methods: Patients with BC that underwent cystectomy from 2000 to 2022 at the Cleveland Clinic Foundation were identified. Patients with NEC at transurethral resection (TUR) or cystectomy, and patients with BC with other pathologies (non-NEC) were selected. pCR was defined as downstaging from tumor presence in diagnostic resection to no residual tumor (pT0N0) after NAC. Survival outcomes of interest included recurrence-free survival (RFS) and OS. Results: A total of 562 cases of BC that underwent RC were identified. Of these, 50 patients included a diagnosis of NEC in their pathology report, either in TUR (n=42), or in RC (n=8) with 36% (18/50) of them with NEC without an associated conventional urothelial cell carcinoma (UCC), while 502 patients were diagnosed with UCC, with or without variant histologies and 10 patients with other histologies without UCC. Among patients with NEC, median age was 69 and M:F-45:5. When NEC patients were compared to non-NEC BC patients, they were more likely to present with muscle invasive bladder cancer (MIBC), (83% vs 60%; p=0.003) and receive NAC (86% vs 35%; p<0.001) Most common chemotherapy regimen used in NEC patients was combination platinum and etoposide (26/36), compared to platinum and gemcitabine in non-NEC BC patients (141/184). pCR rate was 36% (13/36) in NEC, compared to 20% (36/184) in non-NEC cohort. (p=0.046). In terms of survival outcomes, RFS and OS were similar between the two groups (log-rank p-values 0.08 and 0.14, respectively). Conclusions: NAC prior to RC is beneficial in NEC of the bladder as a higher proportion achieve pCR when compared to non-NEC BC. In our cohort, despite presenting with more advanced disease, oncologic outcomes after NAC with RC were similar between the two groups. [Table: see text]