Primary sarcomas of urinary bladder: A SEER analysis.

878 Background: Primary bladder sarcoma (PBS) is a rare entity. In this study, we analyzed demographics, clinical characteristics, and survival outcomes of PBS using the Surveillance, Epidemiology and End Results (SEER) database. Methods: We identified patients with urinary bladder sarcoma in the SEER database from the years 2000 to 2020 using the primary cancer site codes for urinary bladder as well as histological codes (ICD-O-3) that match the list of sarcoma histology found in the NCCN soft tissue sarcoma and bone cancer guidelines. Data for demographics, disease extent, median overall survival (OS), and treatment modalities were obtained. Sarcomas mixed with carcinomas, so-called carcinosarcomas, were included in the analysis. From the same database, OS data on urothelial carcinomas were obtained for comparison. Results: During the period of analysis, a total of 349,326 patients with primary bladder neoplasms were identified. Among them, 707 (0.002%) patients had PBS. The majority were Caucasian (71.9%) followed by Hispanics (12.9%) and African Americans (11.0%). There were 445 males (62.9%) with PBS. The most common histology was carcinosarcoma (40.9%), followed by leiomyosarcoma (20.4%), rhabdomyosarcoma (13%), and unspecified sarcoma (9.3%). Among the 654 patients with known extent of disease, 56.7%, 24.9%, and 18.3% had localized, locoregional, and distant metastatic disease, respectively. OS for patients with localized, regional, and distant diseases were 32, 12, and 4 months, respectively (P<0.0001). Bladder sarcomas were associated with worse survival than urothelial carcinomas (14 months vs. 92 months, P<0.01). OS was longer in patients with pure sarcomas compared to patients with mixed sarcomas (26 months vs. 9 months, P< 0.001). Among the 697 patients with treatment data available, 34 (4.9%) received chemotherapy only, 468 (67.1%) received surgical resection only, 152 (21.8%) received both, and 43 (6.2%) received neither. Both chemotherapy and surgery were associated with longer median OS. Those who received chemotherapy showed a median OS of 42 months compared to 9 months seen in the no chemotherapy group (P<0.001). As for surgical resection, median OS of those who underwent surgery was 16 months compared to 8 months in those who did not (P=0.014). Conclusions: Bladder sarcomas are rare and associated with worse outcomes when compared to urothelial carcinoma. Carcinosarcomas are associated with worse survival when compared with pure sarcomas. More than half of the bladder sarcomas were diagnosed as localized disease and survival was better when compared with locoregional or distant disease. Chemotherapy and surgical resection were associated with longer median OS, but prospective studies are needed to ascertain these findings after controlling for confounders.