Patient with carcinoma in situ (CIS) will receive further maintenance therapy with 3 consecutive weekly EOquin instillations at the following time points: 3, 6, 12, 18, and 24 months from the date of TUR. At 3-month follow up visit patients will undergo cystoscopic bladder biopsy and urine cytology. If bladder biopsy is negative at 3-month visit, the follow up during the remaining visits will be by cystoscopy and urine cytology only, which will be done prior to the start of maintenance therapy. In case of positive cytology presence of CIS has to be confirmed histologically with biopsies.