Carcinosarcoma is an aggressive subtype of bladder cancer: A population‐based study

BACKGROUND: Case reports of bladder carcinosarcoma (BCS) indicate high rates of recurrence and metastasis and poor prognosis. However, the differences in clinicopathologic characteristics and prognosis between BCS and conventional bladder cancer histologies (transitional cell carcinoma [TCC], squamous cell carcinoma [SCC] and adenocarcinoma [AC]) have not been fully clarified in a large study. Therefore, we conducted a large population‐based study to further investigate these differences. PATIENTS AND METHODS: Information on patients with BCS and conventional bladder cancer (TCC, SCC or AC) was extracted from the Surveillance, Epidemiology, and End Results database. Categorical variables were compared using Pearson's chi‐squared test or Fisher's exact test. Survival analysis was carried out using the Kaplan–Meier method, and differences in survival were assessed using the log‐rank test. Propensity score matching analysis was conducted to calibrate the differences between the baseline characteristics, after which Cox regression analysis was applied to calculate the hazard ratios and 95% confidence intervals of BCS compared to other subtypes. Subgroup analysis and related interaction were tested to evaluate the consistency and heterogeneity of results. RESULTS: We enrolled 152 patients with BCS and 180,196 patients with TCC, SCC or AC. Our results showed that BCS was associated with poor differentiation, advanced stage and an unfavourable overall survival and cancer‐specific survival. BCS had a worse prognosis than TCC and AC, but no statistically significant difference in survival was noted between BCS and SCC. CONCLUSIONS: BCS is a more aggressive bladder cancer than TCC and AC but is comparable to SCC. These findings broaden our understanding of BCS and may be helpful in clinical practice.