Trying to Find the Correct Length of Treatment With Immune Checkpoint Therapy

* Documentation of disease

  * Histologic documentation: Histologically or cytologically confirmed urothelial carcinoma (UC) with predominantly transitional-cell features
  * Stage: Locally advanced or metastatic disease prior to starting immune checkpoint blockade
  * Tumor Site: Bladder, renal pelvis, ureter, urethra, or prostate
* Patients must have received at least one cycle of current active treatment with standard of care (SOC) Food and Drug Administration (FDA) approved PD-1/L1 immune checkpoint inhibitor (ICI)-containing therapy for locally advance or metastatic UC
* Patients without progressive disease per Response Evaluation Criteria in Solid Tumors (RECIST) version (v) 1.1 guidelines (i.e., with an ongoing \[complete response\] CR, partial response \[PR\], or stable disease \[SD\]) following completion of 12-15 months of ICI treatment
* No history of tuberculosis, active hepatitis B (HBV) or hepatitis C (HCV), or uncontrolled human immunodeficiency virus (HIV)

  * Patients with resolved HBV infection, defined as positive hepatitis B core antibody (anti-Hb) and negative hepatitis B surface antigen (HbsAg), are eligible
  * Patients with positive HCV antibody are eligible if HCV ribonucleic acid (RNA) polymerase chain reaction (PCR) is negative
  * Patients with HIV who are compliant with highly active antiretroviral therapy (HAART) and have normal CD4 count and undetectable viral load are eligible
* No history of allogeneic organ transplantation
* No current immunosuppressive medication exceeding 10 mg/day of prednisone or its equivalent

  \* Patients with pre-existing or treatment-emergent autoimmune or inflammatory disorders which do not require systemic immunosuppressive treatment exceeding 10 mg/day of prednisone or its equivalent may be included
* No history of another primary malignancy except for malignancy treated with curative intent with no known active disease for \>= 2 years, and adequately treated non-melanomatous skin cancer or carcinoma in situ (e.g. cervical carcinoma in situ \[CIS\]) without evidence of disease
* No female patients who are pregnant or breastfeeding, or male or female patients of reproductive potential who are not willing to employ effective birth control, because this study involves investigational agents whose genotoxic, mutagenic, and teratogenic effects on the developing fetus and newborn are unknown. Therefore, for women of childbearing potential only, a negative urine or serum pregnancy test pregnancy test done =\< 14 days prior to registration is required

REGISTRATION ELIGIBILITY CRITERIA:

* Patients without progressive disease per RECIST v 1.1 guidelines (i.e., with an ongoing CR, PR or SD) following completion of 12-15 months of ICI treatment
* No toxicity from ICI therapy that makes continuation of treatment clinically unacceptable
* Adequate bone marrow and organ functions to continue PD-1/L1 ICI as judged by the treating physician
* Age \>= 18 years
* Eastern Cooperative Oncology Group (ECOG) performance status 0-2
* Central nervous system (CNS) metastasis is allowed if radiographically stable, clinically asymptomatic, and prior local therapy (if received) was completed \> 6 months before registration
* No history of tuberculosis, active hepatitis B (HBV) or hepatitis C (HCV), or uncontrolled human immunodeficiency virus (HIV)

  * Patients with resolved HBV infection, defined as positive hepatitis B core antibody (anti-Hb) and negative hepatitis B surface antigen (HbsAg), are eligible
  * Patients with positive HCV antibody are eligible if HCV RNA PCR is negative
  * Patients with HIV who are compliant with highly active antiretroviral therapy (HAART) and have normal CD4 count and undetectable viral load are eligible