Testing the Addition of an Anti-Cancer Drug, Gemcitabine, to Usual Treatment (BCG Alone) in People Whose Non-Muscle Invasive Bladder Cancer (NMIBC) Came Back After Prior BCG Therapy

Inclusion Criteria: * Documentation of Disease: Histologic confirmation of urothelial carcinoma that is high grade Ta, high grade T1, or Tis (Tis/carcinoma in situ \[CIS\] only disease) within 120 days prior to randomization * Any component of neuroendocrine carcinoma (i.e., small cell or large cell) is not allowed. Other histologic subtypes/variant histologies are allowed so long as there is a predominantly urothelial component. \* Note: Pure squamous cell carcinoma or pure adenocarcinoma without a urothelial component are not allowed * All visible papillary lesions must be macroscopically resected by TURBT within 90 days of randomization. (Residual CIS is permitted). \* If the treating urologist did not perform the TURBT, the treating urologist must perform a cystoscopy within 45 days prior to randomization to confirm the absence of visible papillary disease * All patients with high grade T1 must undergo a restaging TURBT within 90 days of randomization. Patients who undergo a restaging TURBT that shows no residual cancer in the specimen are still eligible for trial based on prior TURBT * Patients must have BCG-Exposed non muscle invasive bladder carcinoma (NMIBC), defined as recurrent high grade NMIBC within 24 months of last BCG exposure but not meeting the definition of BCG unresponsive disease * Note: Up to 26 months from the last BCG instillation is allowed for the treating physician to perform a transurethral resection of bladder tumor (TURBT) so long as the…