Clinical and urodynamic indicators of non-response to OnabotulinumtoxinA in idiopathic overactive bladder

Background: Onabotulinum toxin-A (BoNT/A) intradetrusor injection is an established, effective, and safe treatment for overactive bladder (OAB) refractory to anticholinergics. Although primary non-response to BoNT/A is infrequent, it remains clinically relevant. We investigated whether baseline clinical, demographic, or urodynamic characteristics could predict non-responders prior to treatment. Methods: A Retrospective analysis of 65 consecutive refractory idiopathic OAB (I-OAB) male and female patients treated with 100 U BoNT/A at Jewish General Hospital between 2005 and 2015 was conducted. Response defined as >30% increase in maximum cystometric bladder capacity (MCBC) at 12 weeks, confirmed clinically and through urodynamic studies (UDS). Non-response was verified by lack of improvement after the second intradetrusor injection. Results: A total of 13 men and 52 women with a mean age of 70 years (range 21 to 94) were studied. At 12 weeks, 63% (41/65) of patients demonstrated a significant response in both symptoms and UDS (p < 0.05), while 37% (24/65) were non-responders. Non-responders exhibited significantly higher baseline first desire to void volume (FDV) and postvoid residual urine (PVR) (p < 0.05), with a trend toward greater bladder compliance (18.8 ± 15.1 vs. 13.3 ± 9.4 cmH2O, p = 0.09). Multivariate logistic regression identified no independent predictors of response. Conclusions: Elevated baseline FDV and PVR are associated with poor response to 100 U BoNT/A in refractory I-OAB patients.