Infliximab or Vedolizumab in Treating Immune Checkpoint Inhibitor-Related Colitis in Patients With Genitourinary Cancer or Melanoma

Inclusion Criteria: * Patients who receive any type of immune checkpoint inhibitor (ICI) therapy * Patients with peak grade \>= 2 immune-related diarrhea and/or colitis (according to the Common Terminology Criteria for Adverse Events (CTCAE) version 5.0 within 45 days prior to initiation of study treatment (infliximab/ vedolizumab) * Patients with ability to understand and willingness to sign informed consent * Patients with genitourinary cancer or melanoma or non-small cell lung cancer * No concern for active concomitant GI infection for immune-related diarrhea and/or colitis work up at the time of protocol therapy initiation as confirmed by stool tests or as per the treating physician based on clinical presentation * Patient who has been cleared for enrollment by Infectious Diseases consultant or treating physician if positive infection workup or screening tests (e.g. lifelong positive T-spot due to BCG inoculation, chronic colonization) prior to initiation of diarrhea/colitis treatment Exclusion Criteria: * Patients younger than 18 years of age * Patients with persistent gastrointestinal infection confirmed with positive testing despite completing 5 days of antibiotics * Patients are on concurrent immunosuppressive therapies other than what will be given for colitis * Patients with preexisting activehistory of inflammatory bowel disease and/or radiation enterocolitis with active disease status at the time of study treatment initiation * Pregnant and breastfeeding women, and * Women of child-bearing potential who have positive urine or serum pregnancy test or refuse to do pregnancy test unless last menstrual cycle was \> 1 year prior to consent and/ or clear documentation states that patient is peri- or post-menopausal or there was recent supporting objective evidence of 'no pregnancy' status (e.g. blood or imaging) within 30 days prior to initiation of study treatment * Patients who develop concurrent non-GI toxicity at the time of study treatment initiation