Long-term complete response in small cell bladder carcinoma treated with carboplatin, etoposide, and atezolizumab

Background: Small cell bladder carcinoma (SCBC) is a rare and aggressive malignant tumor with no established treatment guidelines. Its treatment algorithm has been based on the small cell lung cancer (SCLC) guidelines. Metastatic SCBC has poor prognosis (even when treated with platinum-based chemotherapy, which is usually used for extensive-disease SCLC). Case presentation: Herein, we report a case of a 71-year-old man with SCBC who underwent radical cystectomy and received adjuvant chemotherapy with gemcitabine and cisplatin. However, recurrent tumors were found 6 months postoperatively. The patient was then treated with carboplatin, etoposide, and atezolizumab and achieved complete response. He continues receiving maintenance therapy with atezolizumab monotherapy without any evidence of recurrence over the 12 months follow up. Conclusion: To our knowledge, this is the first case of metastatic SCBC where carboplatin, etoposide, and atezolizumab achieved long-term complete response.