The clinical impact of routine bladder biopsy after BCG treatment of high grade non muscle invasive bladder cancer.

438 Background: The need for invasive and costly routine bladder biopsies after an induction course of intravesical Bacillus Calmette-Guerin (BCG) in patients with high-grade non-muscle invasive bladder cancer is being questioned. Previous studies focused on differences in tumor detection between cystoscopic, cytologic and histologic results, whereas the clinical impact was disregarded. The aim of this study is to determine the impact of routine bladder biopsies on treatment. Methods: This retrospective multicenter trial included 348 patients from four hospitals in the Netherlands, who had had their BCG therapy evaluated by routine bladder biopsies between 2005 and 2014. The results of urethrocystoscopy (UCS) and/or cytology were compared to pathology outcomes. The influence of malignancies missed by UCS and/or cytology on further treatment was analyzed in 348 patients and in subgroups of patients with and without carcinoma in situ (CIS). A number needed to test was calculated. Secondary outcomes were cos...