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Urodynamic results do correlate with treatment outcomes in idiopathic overactive bladder treatment, at least with onabotulinumtoxin A (Botox). Surprisingly, despite all the urodynamic studies done in OAB, this is new information.
"Despite a really large amount of literature on the various interventions for failed or even treated overactive bladder, very few studies looked at both clinical outcomes and urodynamic outcomes," said Eric S. Rovner, MD, professor of urology at the Medical University of South Carolina in Charleston.
Dr. Rovner, reporting at the 2010 AUA annual meeting in San Francisco, presented urodynamic findings from a multicenter study of intradetrusor injection of onabotulinumtoxin A for OAB, following on last year's presentation of the study's clinical results.
Urodynamic studies were performed at baseline and weeks 12 and 36 in a standardized way, and all the studies were read by an independent central reader to confirm the urodynamic results from the different investigators and sites. In all, 77% of patients across the treatment groups had detrusor overactivity at baseline. The primary outcome of the study was the change in the number of urinary incontinence episodes per week at week 12.
At week 12, the urodynamic parameters, like the primary clinical outcome, generally followed a dose-response relationship. Baseline maximum cystometric capacities ranged from 250 mL to 270 mL. Those increased from 50 mL in the placebo group to 130 mL in the group receiving the 300-U dose. At week 36, there were still some dose-related effects, although they were considerably attenuated.
The change in volume to the first involuntary detrusor contraction at week 12 also showed "somewhat" of a dose-response relationship, Dr. Rovner said. At baseline, that volume ranged from 130 mL to 180 mL, increasing from 40 mL for the placebo group to 100 mL for the 300-U group. Some effect, also dose related, remained at week 36 for all who received active treatment.
UTI most common adverse event
The most common adverse events were urinary tract infections, ranging from 34% to 48% in the active treatment groups, likely related to increased postvoid residual urine volumes (PVRs). Urinary retention, defined as a PVR >200 mL, ranged from 9% to 28% in the treatment groups. However, only 11% to 20% of patients receiving active treatment required or were offered intermittent catheterization.
"Urodynamics do seem to correlate with clinical efficacy, at least with respect to reduction in urge incontinence episodes," Dr. Rovner noted.
He concluded that onabotulinum toxin A is effective in treating idiopathic OAB whether measured by reduction in urge incontinence episodes or improved urodynamic parameters. The effects are maintained but considerably attenuated at 36 weeks.
Dr. Rovner discloses that he has financial and other relationships with Allergan, which funded the study.