Atezolizumab in Treating Patients With Recurrent BCG-Unresponsive Non-muscle Invasive Bladder Cancer

Inclusion Criteria: * Patients must have histologically proven, recurrent, non-muscle invasive urothelial carcinoma of the bladder within 60 days prior to registration; the carcinoma must be stage T1 high-grade, stage CIS, or stage Ta high-grade * Patients with mixed urothelial carcinoma and a glandular and/or squamous component will be eligible for the trial, but the presence of other histologic variants, pure adenocarcinoma, or pure squamous cell carcinoma, or pure squamous carcinoma in situ will make a patient ineligible * Patients must have had all visible tumor resected completely within 60 days prior to registration; CIS disease is not expected to be completely excised; all patients must have tumor tissue from the histologic diagnosis of recurrence available for central pathology review submission; failure to submit these materials will make the patient ineligible for this study * Patients must have had cystoscopy confirming no visible papillary tumor within 21 days prior to registration; (CIS disease is not expected to have been completely excised); if the transurethral resection of bladder tumor (TURBT) or bladder biopsy falls within 21 days of registration it will fulfill this criterion * Patients must have had urine cytology within 21 days prior to registration; cytology for patients with CIS component is not expected to be negative for malignant cells; if the cytology for male patients with only Ta/T1 disease in the absence of CIS is positive for malignant cells, …