A phase 2 pilot study of water irrigation after transurethral resection of bladder tumor (WATIP) demonstrating safety, feasibility and activity

Purpose Non-muscle-invasive bladder cancer (NMIBC) can recur, partly due to seeding of free tumour cells after transurethral resection of bladder tumour (TURBT). Intravesical chemotherapy post-TURBT can reduce the risk but is used infrequently and inconsistently due to cost, complexity and side effects. The objective of this study was to prospectively assess continuous bladder irrigation using water, which may be a safer and easier alternative with comparable effectiveness. Methods WATIP was a prospective, single-arm phase 2 study of water irrigation during and for at least 3 h after TURBT for bladder tumours noted on imaging or flexible cystoscopy. Participants were assessed clinically for adverse effects and with blood tests within 24 h for sodium, haemoglobin and lactate dehydrogenase. The primary endpoints were safety (defined as < 10% adverse events of CTCAE grade >= 3), and feasibility (defined as the intervention being delivered as planned in > 90% of cases) and secondary endpoint was recurrence-free rates (RFR). Results Water irrigation was delivered as planned in 29 (97%) of 30 participants (median age 67 years, 25 (83%) males). The only adverse event (grade 2) was clot retention in one (3.3%) participant. Water irrigation significantly reduced urothelial cell counts in catheter effluent over time, unlike saline irrigation which did not. RFR was 56.2% (9/16 participants with low-risk NMIBC) at first cystoscopy (median interval 108 days) and 62.5% (5/8 evaluable low-risk NMIBC) at 12 months. Conclusion Water irrigation during and after TURBT is feasible and safe. Prospective assessment of its effect on NMIBC recurrence compared to post-TURBT intravesical chemotherapy is needed before recommending its use in routine clinical practice.