Low-Dose-Rate Brachytherapy Combined With Immune Checkpoint Inhibition in Cancer

Inclusion Criteria: * Participants must have histologically confirmed unresectable stage III or stage IV cutaneous melanoma, stage IV renal cell cancer, and stage IV urothelial cancer. * ECOG performance status 0-2. * Have measurable disease per RECIST v1.1 or iRECIST. Refer to Appendix B * Have the following clinical laboratory values: * Absolute neutrophil count (ANC) ≥ 1500/ μL * Hgb ≥ 9 g/dL * Platelet count ≥ 75, 000/ μL * Total bilirubin ≤ 1.5 x ULN (upper limit of normal) * AST and ALT ≤ 2x ULN * Serum Creatinine \< 2x ULN * Female participants who: * Are postmenopausal for at least 1 year before entering the screening visit, OR * Are surgically sterile, OR * Agree to practice true abstinence from heterosexual contact or agree to use effective contraception without interruption during the study therapy and 90 days after the last dose. * Male participants who: * Are surgically sterile, OR * Agree to practice true abstinence from heterosexual contact or agree to use effective contraception without interruption during the study therapy and 90 days after the last dose. Exclusion Criteria: * Participants diagnosed with uveal melanoma * Participants who have been treated with whole head radiation for brain metastases * Invasive cancers not being treated on this trial (i.e. lymphoma that received systemic therapy) diagnosed \< 3 years prior that required systemic treatment. This is intended to include a patient with melanoma who was diagnosed \< 3 …