Hypothesis / aims of study
Intradetrusor botulinum toxin type A (BoNT-A) is an effective third-line treatment for refractory overactive bladder (OAB). It is traditionally administered through multiple injection sites (10–20) to optimize drug distribution. However, the optimal number of injections remains unclear, and simplified strategies could improve procedural efficiency without compromising outcomes. In addition, the reproducibility of the therapeutic effect in repeated treatments has been scarcely evaluated in real-world clinical practice.
Objective:
To compare the clinical efficacy of a reduced strategy (4 injection sites) versus a standard strategy (10 injection sites), and to assess reproducibility of treatment effect through intraindividual analysis.
Study design, materials and methods
This was a prospective observational real-world study including 84 treatment episodes in 66 patients with OAB treated with intradetrusor BoNT-A. The procedure was performed by outpatient rigid cystoscopy under standard aseptic conditions. In the reduced-template group, BoNT-A was injected intradetrusor at 4 sites distributed across the bladder wall (right lateral wall, left lateral wall, and two posterior wall/base sites), avoiding the trigone. Correct placement was confirmed by visible wheal formation. The following variables were analysed: nocturia, daytime urinary frequency, voided volume, postvoid residual, bladder capacity, and time to retreatment. Intragroup comparisons were performed using the Wilcoxon test, intergroup comparisons using the Mann–Whitney test, survival analysis using Kaplan–Meier curves, and Cox regression analysis. An intraindividual analysis was also performed in patients who underwent repeated treatments.
Results
Both groups were comparable at baseline. A significant improvement in nocturia was observed in both the 4-injection group (p=0.007) and the 10-injection group (p<0.001), with no differences between strategies in any of the functional parameters analysed, including daytime urinary frequency, voided volume, postvoid residual, and bladder capacity (p>0.05). No differences were found in retreatment-free survival (log-rank p=0.744). In multivariable analysis, the number of injection sites was not associated with retreatment risk (HR 0.723; p=0.793), whereas diabetes was an independent predictor (HR 14.369; p=0.019). Intraindividual analysis showed consistent results across repeated procedures, confirming the reproducibility of the therapeutic effect.
Interpretation of results
In this real-world cohort, reducing the number of intradetrusor BoNT-A injection sites from 10 to 4 did not appear to compromise clinical efficacy or treatment durability. Functional outcomes and retreatment-free survival were comparable between both strategies, suggesting that therapeutic response may depend more on patient-related factors than on the injection template itself. The finding that diabetes independently predicted retreatment supports this interpretation. In addition, the intraindividual analysis showed consistent results across repeated procedures, reinforcing the reproducibility of BoNT-A efficacy in routine practice. Overall, these results support procedural simplification as a feasible strategy, although controlled prospective studies are needed to confirm these findings.