Integrated Clinical and Genomic Assessment of Small Cell Bladder Carcinoma Using Population-Based and Mutational Data

Background Small cell carcinoma of the bladder (SCCB) is rare, with unclear clinical and prognostic features. This study aims to identify factors influencing SCCB prognosis and develop a predictive clinical model. Materials and Methods Data from the SEER database (2004–2015) were analyzed. The Cox regression analyses identified prognostic factors for overall survival (OS) and cancer-specific survival (CSS). To predict the prognosis of SCCB, we used COX combined with LASSO regression to select variables for constructing nomograms, and compared survival outcomes of high- and low-risk score groups using Kaplan-Meier (KM) curves. We evaluated the model by using ROC curves, calibration curves, and DCA. Results SCCB patients had advanced tumor stages at diagnosis, with significantly poorer OS (15 vs. 22 months, P < 0.001) and CSS (18 vs. 30 months, P < 0.001) compared to transitional cell carcinoma (TCC). Chemotherapy and radical cystectomy (RC) were independent protective factors. The nomogram for OS and CSS included TNM stage, M stage, and chemotherapy, with age included only in the OS model. High-risk SCCB patients had significantly shorter OS (9 vs. 31 months, P < 0.001) and CSS (10 vs. 59 months, P < 0.001). TP53 (88%) and RB1 (76%) were the most common mutations in SCCB. Conclusion SCCB is more aggressive and has poorer outcomes compared to TCC. This study provides a reliable nomogram for personalized prediction of OS and CSS in SCCB patients. Both chemotherapy and RC can significantly improve the prognosis of SCCB. TP53 and RB1 may be potential therapeutic targets.