The aim of this work was to clarify and extend the existing clinical guidelines on organ-sparing treatment of muscleinvasive bladder cancer. The standard protocol of radical conservative treatment for muscle-invasive bladder cancer includes transurethral resection of the bladder, external beam radiotherapy with simultaneous chemotherapy (radiosensitization), which is usually referred to as trimodal therapy. The implementation of trimodal therapy into routine practice in Russia is limited due to the lack of distinct criteria for each of the stages. The involvement of surgeons, radiation oncologists, and chemotherapists, on the one hand, provides the required multidisciplinary approach to cancer treatment; on the other hand, it might impede the entire algorithm. To address this problem, specialists from the Department of Radiology (project moderators), Department of Cancer Urology, and Department of Chemotherapy of N.N. Petrov National Medical Research Center of Oncology under the auspices of Saint Petersburg Oncological Research Society formed a group of experts, including radiation oncologists, urologists, and chemotherapists from federal and local cancer (educational) institutions of Saint Petersburg who had an experience of treating muscle-invasive bladder cancer. The guideline was developed with the consideration of available guidelines published by leading professional associations of radiotherapy and oncology (urological), research articles, and own experience.