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Small cell carcinoma of the bladder is very rare, accounting for less than 5% of all bladder cancer. It has a poor prognosis driven from its aggressive clinical feature. Due to its rarity, there is no established standard treatment yet.

We retrospectively reviewed patients treated with non-metastatic small cell carcinoma of the bladder at 2 tertiary hospitals between 2005 and 2021. We evaluated patient characteristics, treatment performed, and subsequent clinical outcomes.

A total of 24 patients were included. The median age was 65 years (range, 40-91 years), and 7 patients (29.2%) had pure-histology of small cell carcinoma while others had mixed pathology (small cell predominant). The median overall survival (OS) of all patients was 71.6 months (95% CI, 21.6-121.6 months), each of which was 71.6 months (95% CI, 21.2-122.0 months) for node-negative and 26.3 months (95% CI, 11.5-41.1 months) for node-positive patients. Among 17 patients with N0 disease, 11 received radical cystectomy (RC) (neoadjuvant chemotherapy (NAC): 2; RC only: 7; adjuvant chemotherapy: 2) and 6 received NAC followed by chemoradiotherapy (CRT). Patients who underwent RC did not achieve median OS, and those who underwent CRT had a median OS of 71.6 months (P=0.884). Among 7 patients with node-positive, 4 received RC (NAC:1; RC only:1; adjuvant chemotherapy: 2), 2 received chemotherapy only, and 1 received CRT, with the median OS of 19.4, 26.3 and not-reached, respectively. Upfront chemotherapy was performed in 12 patients (50%) using etoposide/cisplatin in 7 and gemcitabine/cisplatin in 5 patients, and patients who underwent upfront chemotherapy showed longer OS than in those who did not (median OS: 71.6 vs. 43.6 months; P=0.561). Among 15 patients who received RC, 7 patients with neo- or adjuvant chemotherapy showed longer OS than those who did not receive any chemotherapy (median OS: 43.6 months vs. not-reached; P=0.437). Sixteen patients (66.7%) experienced treatment failures, most of them was distant metastasis in 10 followed by pelvic nodal recurrence in 1, and local failures in 5 patients.

Patients with non-metastatic small cell carcinoma of bladder had excellent long-term survival. Node-negative patients showed better survival than node-positive patients. RC with neo-/adjuvant chemotherapy or CRT may be considered in bladder-confined disease. Large well-designed study is warranted to find the optimal treatment.