A Study of TAR-200 in Combination With Cetrelimab Versus Concurrent Chemoradiotherapy in Participants With Muscle-invasive Bladder Cancer (MIBC) of the Bladder

Inclusion Criteria:

* Ineligible for or have elected not to undergo radical cystectomy
* All adverse events associated with any prior surgery and/or intravesical therapy must have resolved to Common Terminology Criteria for Adverse Events (CTCAE) version 5.0 Grade less than (\<) 2 prior to randomization
* Eastern Cooperative Oncology Group (ECOG) performance status Grade 0, 1, or 2
* Thyroid function tests are within the normal range per investigator assessment (or stable on hormone supplementation). Investigators may consult an endocrinologist for participant eligibility assessment in the case of equivocal or marginal test results
* Adequate bone marrow, liver, and renal function: Bone marrow function (without the support of cytokines or erythropoiesis-stimulating agent in preceding two weeks): Absolute neutrophil count (ANC) greater than or equal to (\>=) 1,500/cubic millimeters (mm\^3); Platelet count \>=80,000/mm\^3; Hemoglobin \>=9.0 grams per deciliter (g/dL); Liver function: (Total bilirubin less than or equal to (\<=) 1.5 \* upper limit of normal (ULN) or direct bilirubin \<= ULN for participants with total bilirubin levels greater than (\>)1.5\*ULN (except participants with Gilbert's Syndrome, who must have a total bilirubin \< 3.0 mg/dL), and Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) less than or equal to (\<=) 2.5\* institutional ULN); Renal function: Creatinine clearance \>=30 mL/min using the Cockcroft-Gault formula. 24-hour creatinine clearance test will also be accepted for estimating renal function in situations where Cockcroft-Gault formula is not a good predictor of estimating adequate renal function

Exclusion Criteria:

* Must not have had urothelial carcinoma or histological variant at any site outside of the urinary bladder. Ta/T1/Carcinoma in situ (CIS) of the upper urinary tract (including renal pelvis and ureter) is allowable if treated with complete nephroureterectomy more than 24 months prior to initiating study
* Must not have diffuse CIS based on cystoscopy and biopsy. Diffuse, or multi-focal, CIS is defined as the presence of at least 4 distinct CIS lesions in the bladder at the time of the Screening re-TURBT
* Participants must not have evidence of cT4b, or N1-3, or M1 disease based on local radiology staging (chest, abdomen, and pelvis must be performed using Computed tomography \[CT\] or Magnetic resonance imaging \[MRI\]) within 42 days prior to randomization
* Presence of any bladder or urethral anatomic feature that, in the opinion of the investigator, may prevent the safe placement, indwelling use, or removal of TAR 200
* Evidence of bladder perforation during diagnostic cystoscopy. Participant is eligible if perforation has healed prior to randomization