The researchers used a Markov decision analysis model to examine the cost-effectiveness of intradetrusor botulinum toxin injection, which is not FDA-approved for the treatment of urge incontinence, versus anticholinergic medications. Estimates for treatment efficacy and adverse events, along with utility values for quality of life associated with continence and urge incontinence, were based on published data. The incremental cost-effectiveness ratio (ICER) was calculated as the primary outcome measure and compared to a value of <$50,000 per quality-adjusted life year (QALY), which represents an accepted threshold for defining cost-effectiveness of a therapeutic intervention.
While the cost of botulinum toxin treatment over 2 years was about 70% higher than that of anticholinergic medication ($4,392 vs. $2,563), the intradetrusor injection strategy was also more effective. Based on the ICER, botulinum toxin injection was cost-effective compared to anticholinergic medication (calculated ICER = $14,377/QALY).
In one-way sensitivity analyses examining the effects of varying the model estimates across their ranges, botulinum toxin remained cost-effective unless the cost of the procedure more than doubled or patients became highly compliant with anticholinergic medications.
Neither of these scenarios, however, seems likely, said first author Jennifer M. Wu, MD, MPH, assistant professor of urogynecology at Duke University, Durham, NC.
"Historically, cost-effectiveness of new treatments relative to existing modalities has not been widely studied in the United States," said Dr. Wu, who worked on the study with Anthony G. Visco, MD, and colleagues. "However, it is a topic of growing importance, given rising health care costs.
"Botulinum toxin A injection has recently emerged as a promising new treatment for urge incontinence, and our study supports that it would be a cost-effective option over the 2-year time frame of this analysis. However, it will be important to revisit this issue when long-term outcomes data are available, especially regarding the effectiveness and potential side effects after multiple, repeat botulinum injections."
Dr. Wu observed that the study is also limited by a lack of high quality data on the quality of life effects of urge incontinence and treatment-related adverse events. This is important, considering that the sensitivity analyses also found that anticholinergics would become cost-effective compared to botulinum toxin if the utility value for urinary incontinence was 0.88 versus the value of 0.73 used in the base-case model.
"More utility data in this field are needed to conduct a more rigorous cost-effectiveness analysis. This information could potentially change the cost-effectiveness outcomes," Dr. Wu said.
"For example, one potential adverse event after botulinum is urinary retention. We do not know the impact of urinary retention and the need for self-catheterization on quality of life, and this factor could potentially impact the results of the model."
The analysis was conducted from a societal cost perspective, which Dr. Wu noted was preferable to using a health care system or patient-oriented perspective. While treatment costs included indirect costs for adverse event management, lost productivity associated with the primary treatment and adverse event management were not included due to a lack of relevant data.
The base-case model for the cost-effectiveness analysis assumed the cost of the botulinum procedure was $1,690. In the sensitivity analysis, anticholinergic medication became cost-effective compared to botulinum toxin if the cost per injection procedure rose above $3,875.
"The higher cost of the botulinum procedure assumes that the injection is performed in the operating room. Since this treatment is typically performed in the office setting, it seems doubtful that the cost would rise to the point where botulinum is no longer cost-effective," Dr. Wu said.
Compliance with anticholinergic medication was the other parameter that made a difference in the sensitivity analysis. However, the anticholinergic medications became cost-effective compared to botulinum toxin only when compliance exceeded 75%. The base-case model assumed a compliance rate of 33%.
"Published data indicate compliance with anticholinergic medications for urge incontinence treatment is relatively poor," Dr. Wu told Urology Times. "We do not know whether this is secondary to side effects, lack of efficacy, or poor patient education. At this point, it is less likely that compliance would exceed 75%; however, if this were to occur, then anticholinergics may become cost-effective."
For acquisition cost of anticholinergic medications, the base-case model used brand-name extended-release products; however, the lowest cost of therapy was based on the cost of generic anticholinergics, which did not affect the outcome. Drastic modifications in the inputs for efficacy of botulinum toxin, efficacy of anticholinergic medications, or the incidence of urinary retention associated with botulinum toxin also had no effect on the cost-effectiveness of botulinum toxin when compared to anticholinergic medications.