Surgery With or Without Postoperative Intensity Modulated Radiation Therapy in Treating Patients With Urothelial Bladder Cancer

Inclusion Criteria (A patient cannot be considered eligible for this study unless ALL of the following conditions are met.): * Initial histological diagnosis of muscle invasive urothelial carcinoma * Patients must have undergone a radical cystectomy (reconstructed urinary diversion may be non-continent diversions (eg, ileal conduits) or continent non-orthotopic catheterizable diversions (eg, Indiana pouch) or continent orthotopic diversions (eg, Studer pouch or neobladder)for urothelial bladder carcinoma within 105 days prior to registration. Final cystectomy pathology must be either pure urothelial carcinoma or dominant urothelial carcinoma with admixture of other histologies excluding small cell variants. * Neoadjuvant (preoperative) or adjuvant (postoperative) chemotherapy for the bladder cancer is permitted; however, all patients, even those who will receive adjuvant chemotherapy, must be registered within 105 days after completing cystectomy regardless of whether adjuvant chemotherapy has started. Patients who will be receiving adjuvant (postoperative) chemotherapy will be randomized within 28 days of completing that chemotherapy. * Patients with the following pTNM stages per the American Joint Committee on Cancer (AJCC) 7th ed. are eligible: * pT3apN0; pN1; pN2 provided less than 10 nodes dissected and/or positive surgical margins * pT3bpN0; pN1; pN2 * pT4apN0; pN1; pN2 * pT4bpN0; pN1; pN2 * Appropriate stage for study entry based on the following diagnosti…