Inclusion Criteria:

          -  PRE-REGISTRATION ELIGIBILITY CRITERIA

          -  Histologically confirmed muscle-invasive urothelial carcinoma of the bladder or upper
             tract; variant histology allowed as long as urothelial carcinoma is predominant (>
             50%); pure small-cell carcinoma is excluded

          -  Paraffin tissue samples obtained by transurethral resection of muscle-invasive bladder
             tumor, upper tract resection, cystectomy/nephrectomy/ureterectomy, or
             nephroureterectomy must be available; this specimen submission is mandatory prior to
             registration as results will be used for stratification

          -  Patient must fit into one of the following three categories:

               -  Patients who received neoadjuvant chemotherapy and pathologic stage at surgical
                  resection is >= pT2 and/or N+ OR

               -  Patients who are not cisplatin-eligible (according to >= 1 of the following
                  criteria: Eastern Cooperative Oncology Group [ECOG] performance status of 2,
                  creatinine clearance < 60 mL/min, grade >= 2 hearing loss, grade >= 2 neuropathy,
                  or New York Heart Association class III heart failure and pathologic stage at
                  surgical resection is >= pT3 or pN+) OR

               -  Patients that decline adjuvant cisplatin-based or other systemic chemotherapy
                  based on an informed discussion with the physician and pathologic stage at
                  surgical resection is >= pT3 or pN+

          -  Patient must have had radical surgical resection of their bladder cancer >= 4 weeks
             but =< 16 weeks prior to pre-registration

          -  No invasive cancer at the surgical margins

          -  No evidence of residual cancer or metastasis after surgery

          -  No metastatic disease on cross-sectional imaging (according to Response Evaluation
             Criteria in Solid Tumors [RECIST] version [v]1.1 criteria)

          -  No active autoimmune disease or history of autoimmune disease that might recur, which
             may affect vital organ function or require immune suppressive treatment including
             systemic corticosteroids; these include but are not limited to patients with a history
             of immune related neurologic disease, multiple sclerosis, autoimmune (demyelinating)
             neuropathy, Guillain-Barre syndrome, myasthenia gravis; systemic autoimmune disease
             such as systemic lupus erythematosus (SLE), connective tissue diseases, scleroderma,
             inflammatory bowel disease (IBD), Crohn's, ulcerative colitis, hepatitis; and patients
             with a history of toxic epidermal necrolysis (TEN), Stevens-Johnson syndrome, or
             phospholipid syndrome because of the risk of recurrence or exacerbation of disease;
             human immunodeficiency virus (HIV) (+) patients are eligible as long as they have: cd4
             > 200, undetectable viral load and on highly active antiretroviral therapy (HAART)
             therapy

          -  No current pneumonitis or prior history of non-infectious pneumonitis that required
             steroids within the previous 5 years

          -  Patients with vitiligo, endocrine deficiencies including type I diabetes mellitus,
             thyroiditis managed with replacement hormones including physiologic corticosteroids
             are eligible

          -  Patients with rheumatoid arthritis and other arthropathies, Sjogren's syndrome and
             psoriasis controlled with topical medication and patients with positive serology, such
             as antinuclear antibodies (ANA), anti-thyroid antibodies should be evaluated for the
             presence of target organ involvement and potential need for systemic treatment but
             should otherwise be eligible

          -  No known active hepatitis B (e.g., hepatitis B surface antigen [HBsAg] reactive) or
             hepatitis C (e.g., hepatitis C virus [HCV] ribonucleic acid [RNA] [qualitative] is
             detected)

          -  No postoperative/adjuvant systemic therapy

          -  No prior treatment with any therapy on the PD-1/PD-L1 axis

          -  No treatment with any other type of investigational agent =< 4 weeks before
             pre-registration

          -  No major surgery =< 4 weeks before pre-registration

          -  No radiation therapy =< 4 weeks before pre-registration

          -  No neoadjuvant chemotherapy =< 4 weeks before pre-registration

          -  Not pregnant and not nursing

          -  ECOG performance status =< 2

          -  Absolute neutrophil count (ANC) >= 1,200/mm^3

          -  Leukocytes >= 3,000/ mm^3

          -  Platelet count >= 75,000/mm^3

          -  Hemoglobin >= 9 g/dL or >= 5.6 mmol/L

          -  Creatinine =< 2.0 x upper limit of normal (ULN) OR calculated (calc.) creatinine
             clearance >= 30 mL/min

          -  Total bilirubin =< 1.5 x upper limit of normal (ULN)

          -  Aspartate aminotransferase (AST)/alanine aminotransferase (ALT) =< 3.0 x upper limit
             of normal (ULN)

          -  Serum albumin >= 2.8 g/dL

          -  For women of childbearing potential only: a negative urine or serum pregnancy test
             done =< 7 days prior to pre-registration is required

          -  REGISTRATION ELIGIBILITY CRITERIA

          -  Results of central PD-L1 testing available; Q2 Solutions will forward the PD-L1
             results to the statistical center and the statistical center will notify the site that
             the result is available; the notification from the Alliance registration/randomization
             office will serve as a confirmation of this eligibility criteria; after sites receive
             the confirmation e-mail from Alliance they can register the patient