Clinical characteristics, oncologic outcome, and survival in patients with urothelial cancer with pure and partial squamous cell differentiation.

e16612 Background: In bladder cancer (BC) patients, pure (SCC) and partial (PSCC) squamous cell carcinomas belong to the most common histologic subtypes with approximately 5% of cases. They are highly aggressive and curative treatment in a local disease stage is typically radical cystectomy (RC). In case of tumor progression or metastatic disease, only limited data on the optimal treatment algorithm and its efficacy exists. In this study, we present clinical characteristics and oncologic outcome in a large patient cohort of SCC and PSCC. Methods: Between 2003 and 2021, we extracted data from patients with SCC and PSCC histology who received RC due to invasive bladder cancer. Clinical characteristics, treatment patterns, progression free- and overall survival were the primary outcome parameters. Kaplan-Meier curves were calculated for PFS and OS and a log rank test was applied to compare survival curves. Results: Overall, 770 patients were screened of which 26 men and 28 women with a mean age of 68.4 (SD 11.7) and 67.9 years (SD 14) years were identified. Twenty-three patients had SCC and 31 PSCC. No neo-adjuvant treatment was applied compared to 16 adjuvant chemotherapy regimens. Urinary diversion was ileal-conduit in 30 cases, Mainz-pouch in nine, ureterocutaneostomy in eleven, ileal neo-bladder in three and transverse conduit of the colon in one patient. The mean number of extirpated lymphnodes were 22.8 (SD 17.7) with a mean positivity of three (SD 8.3) lymphnodes. Mean follow-up was 11.5 months with a PFS of 5.9 and 8.7 mo. and OS of 13.3 mo. (SD 12.2) and 7.5 (SD 7.8) in men and women, respectively. There was no statistically significant survival difference for men and women as well as SCC and PSCC. Conclusions: This contemporary data demonstrated the aggressive nature of SCC of the bladder with IC being the most common urinary diversion. Compared to data from transitional cell carcinoma, PFS and OS was shorter and application of adjuvant Cx was overall low. Structured novel treatment modalities are urgently needed in this highly aggressive bladder cancer population.