Atezolizumab Plus Etoposide and Platinum in Small Cell Bladder Cancer

The study population will include male and female patients over the age of 18 with invasive (cT1-cT4) small cell / neuroendocrine carcinoma of the bladder (MIBC), with or without urothelial cancer component, who are eligible for platinum based chemotherapy and immunotherapy. All patients will be fit to undergo surgical resection of their cancer by cystectomy. Patients with resectable N1 disease within the true pelvis are eligible. Participants will receive: Atezolizumab 1,200 mg IV Day 1 Etoposide 100 mg/m2 IV on Days 1-3 Carboplatin AUC 5 IV on Day 1 or Cisplatin 70 mg/m2 IV on Day 1 (Patients can be switched at investigator's discretion between cisplatin and carboplatin between cycles. Rationale must be provided.) Repeat q 21 days x 4 cycles Atezolizumab will be administered by intravenous (IV) infusion at a fixed dose of 1200 mg Day 1 of every 21 day cycle with chemotherapy x 4 cycles. Following cystectomy, Atezolizumab maintenance Q 21 days will continue until unacceptable toxicity or loss of clinical benefit as determined by the investigator after an integrated assessment of radiographic and biochemical data, local biopsy results (if available), and clinical status (e.g., symptomatic deterioration such as pain secondary to disease), or up to 1 year (e.g., 16 cycles).