Introduction: Carcinoma in situ (CIS) has a high rate of recurrence despite bacillus Calmette-Guérin (BCG) therapy. Cystoscopy and urine cytology are used for surveillance, but their diagnostic value can be limited by BCG-induced changes. We investigated whether routine bladder biopsy (RB) can increase early detection of CIS persistence and thereby improve patient outcome.

Methods: Patients treated for pure CIS from 2011–2021 were reviewed retrospectively. All patients were treated with transurethral resection of bladder tumor (TURBT) followed by BCG induction and maintenance therapy with standard surveillance. One urologist performed RB in all patients at six months, while all other urologists only performed for-cause biopsy (FC) based on cystoscopic and cytologic abnormalities. Outcomes were compared between RB and FC groups according to an intention-to-treat analysis.

Results: Forty-seven patients were included, of whom 23 had RB and 24 had FC. Median ages were 69 years and 76 years in the RB and FC groups, respectively, and 36 (77%) were male. Median followup was three years and 3.5 years in the RB and FC groups, respectively. High-grade recurrence was observed within six months in five patients (21.7%) in the RB group and two patients (8.3%) in the FC group. There was no significant difference in the rate of high-grade recurrence during the observation period (p=0.197). Progression to muscle-invasive or locally advanced bladder cancer was observed in one patient (4.3%) in the RB group and five patients (20.8%) in the FC group (p=0.09). Limitations include small sample size, retrospective analysis, and irregular use of cytology in the FC group.

Conclusions: In our single-institutional series of patients with pure CIS, there was a trend towards a higher rate of recurrence within six months but lower rate of progression within the study period when patients were managed with RB at six months compared to FC biopsy. This suggests that early detection of persistent CIS may prevent later progression.