Definitive Chemoradiotherapy Versus Radical Cystectomy for Small Cell Carcinoma of the Bladder: A Multicenter Retrospective Study.

INTRODUCTION: To compare oncologic outcomes between radical cystectomy and definitive chemoradiotherapy in patients with nonmetastatic small cell carcinoma of the bladder (SCCB). MATERIALS AND METHODS: We retrospectively reviewed 72 patients with nonmetastatic SCCB treated with curative intent between 2005 and 2021 across 9 tertiary academic institutions. Patients were categorized into a radical cystectomy group (OP, n = 49) or a radiotherapy group (RT, n = 23). Overall survival (OS) and progression-free survival (PFS) were estimated using the Kaplan-Meier method and compared using log-rank tests. To account for baseline imbalances, an IPTW analysis based on propensity scores was performed. RESULTS: The median follow-up duration was 31.3 months. Median OS was 66.2 months in the OP group and 71.6 months in the RT group (P = .305). The 5-year OS rates were 53.6% and 82.6% in the OP and RT groups, respectively. Stage-stratified and IPTW-adjusted analysis likewise showed no significant differences in OS between groups. On multivariable analysis, nodal involvement was independently associated with worse OS (HR, 9.877; 95% CI, 1.07-91.60; P = .044). Upfront chemotherapy showed a trend toward improved OS, although statistical significance was not reached (HR, 0.14; 95% CI, 0.01-2.25; P = .167). Distant metastasis was the predominant failure pattern in both groups. CONCLUSION: Definitive CCRT showed survival outcomes not significantly different from radical cystectomy, though baseline imbalances and small sample size warrant cautious interpretation. Given the predominance of distant failure, systemic chemotherapy remains a key component of treatment, and bladder-preserving CCRT may represent a treatment option for carefully selected patients.