We have developed a novel bladder preservation therapy for patients with muscle-invasive bladder cancer and lymph node metastasis: balloon-occluded arterial infusion (BOAI) of cisplatin/gemcitabine, with concomitant hemodialysis and irradiation [the so-called 'OMC (Osaka Medical College) regimen']. The OMC regimen delivers an extremely high concentration of anticancer agent to the site of the tumor, as well as the pelvic area, without causing any adverse systemic effects. In this study, we investigated the efficiency of the OMC regimen in 34 patients who underwent BOAI with cisplatin (100, 200 or 300 mg) along with 60 Gy of irradiation; patients who failed to achieve CR underwent secondary BOAI with gemcitabine (1,600 mg). The overall clinical response was 73.5% (CR: 35.3%; PR: 17.6%; SD: 20.6%). The 5-year overall and progression-free survival rates were 54.4% and 52.5%, respectively. For treatment failure, N2 stage was selected as a significant risk factor by simple and multiple logistic regression analyses. Cox proportional hazards analyses showed that N2 stage, T4 stage and the presence of hydronephrosis were significant risk factors for overall survival. Indeed, 55.6% of patients with N1 stage achieved a complete response (CR) (vs. 12.5% for N2 patients, p=0.0151), and 90% (9/10) of the CR patients survived without recurrence with an intact bladder after a mean follow-up of 85 (range 7-193) weeks. The 3-year progrssion-free survival rate with an intact bladder was 65.8% (vs. 37.5% for N2, p=0.034), and the 5-year overall survival rate was 71.8% (vs. 30.6% for N2, p=0.004). No patients suffered severe toxicities of Grade II or more; the oldest patient, aged 85 years, successfully completed this therapy. In conclusion, the OMC regimen can be regarded as a new option for patients with macroscopic lymph node involvement, especially those at stage N1. Therapy will improve the feasibility of radical cure even without the need for cystectomy in patients for whom surgery after neoadjuvant chemotherapy would otherwise be necessary, and also facilitate potential cure in patients for whom, otherwise, merely palliative treatment would seem the only option.