The authors of this study describe a ‘real-life’ cohort of patients who underwent intravesical bladder injections of Onabotulinumtoxin A for overactive bladder (OAB) and report on ‘compliance’ with therapy at 3 and 5 years. They note that at 3 years only one-third of patients were still using this treatment. I am concerned that some physicians may discount the use of this therapy given these low rates of continuation.
Fairly large clinical studies with long-term outcomes provide important information to the medical community that often offers a different perspective than that found in the initial pharmaceutical company sponsored studies of a particular drug. On the other hand, such clinical studies may have a number of shortcomings, they are often retrospective, have less rigid ‘entry’ criteria, have less structured follow-up and may reflect one particular surgeon's decision-making process and/or technique.
The ability of Onabotulinumtoxin A to provide relief in many patients with OAB who previously failed all other treatment measures is well documented. In fact in This study, at a very minimum, more than one-third of the patients apparently continued to have treatment success with minimal morbidity 5 years after treatment initiation. The question these authors attempt to address is why two-thirds of the patients discontinued treatment.
I think that the news regarding discontinuation rates is actually better than it sounds from the above description. First, 23/84 that discontinued treatment never had any efficacy from their first treatment and although it is unclear from the data, it would appear that for many this was their only attempt at treatment. I have a difficult time calling a patient who has primary failure of a therapy a ‘drop-out’. To me a ‘drop-out’ implies someone who was successfully treated and then for whatever reason discontinued treatment. Second, patients who had postvoid residual urine volumes (PVRs) of >150 mL were advised to start clean intermittent self-catheterization (CISC). In all, 32 patients who had not previously performed CISC were told to do so. It seems that there might be many who carry somewhat of a residual, even above 150 mL who would be clinically asymptomatic and if not having to do CISC may not have discontinued BT therapy. Third, 23 patients stopped therapy because of problems with UTIs; in 2012, we recognise the importance of prophylactic antibiotics whenever a procedure like this is performed. This may not have been fully apparent when the patients in this study were treated. Potentially, initial prevention of UTI may have permitted more patients to stay with the therapy. Finally, in many patients the original protocol is different than that recommended today. Lower doses than those that were initially used in this study are currently recommended (that may decrease some of the tolerability issues encountered in this study) and general anaesthesia is used much less often during treatment (may, or may not, improve tolerability of procedure).
The authors are to be congratulated for noting many of these limitations in their study. At the end of the day, however, if the patients who were initial failures are taken out of the calculations, if CISC was not recommended for everyone with a PVR of >150 mL, if prophylactic antibiotics were used and if the currently used doses had been given initially, it is likely that the overall discontinuation rate would be significantly lower and the ‘success-rate’ much better.