- Arm I (experimental): Patients receive intravesical mitomycin C over two 30-minute instillations per session, and bladder hyperthermia (42 +/-2°C) is delivered in combination with each instillation. The suspension is maintained in the bladder for up to 2 hours. Treatment repeats once a week for 6 weeks followed by a 6-week rest period. Patients who are disease-free proceed to maintenance therapy consisting of one instillation of mitomycin C with bladder hyperthermia every 6 weeks for 1 year and then once every 8 weeks for 1 year. Patients who are disease-free at 24 months may continue treatment at the discretion of the clinician.