Testing MK-3475 (Pembrolizumab) After Surgery for Localized Muscle-Invasive Bladder Cancer and Locally Advanced Urothelial Cancer

Inclusion Criteria: * PRE-REGISTRATION ELIGIBILITY CRITERIA * Histologically confirmed muscle-invasive urothelial carcinoma of the bladder, urethra, upper tract, or lymph node positive (LN+) disease; variant histology allowed as long as urothelial carcinoma is predominant (any amount of squamous differentiation is allowed); any component of neuroendocrine carcinoma is excluded * Paraffin tissue samples obtained by transurethral resection of muscle-invasive bladder tumor, upper tract resection, or radical cystectomy/nephrectomy/ureterectomy/nephroureterectomy/cystoprostatectomy or urethrectomy must be available; this specimen submission is mandatory prior to registration as results will be used for stratification; specimens from radical/definitive surgery (radical cystectomy/nephrectomy/ureterectomy /nephroureterectomy/cystoprostatectomy and LN dissection) are preferred over transurethral resection, if available * 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 ad…