Cost-effectiveness of new treatments for overactive bladder: the example of tolterodine, a new muscarinic agent: a Markov model

Economic analyses of interventions for chronic diseases require evaluations over a long timeframe to illustrate the benefits and costs of treatments. Clinical trials are generally short and carried out in strictly controlled conditions. They are therefore of limited value for economic evaluation aimed at facilitating decisions about resource allocation. The objective of this study was to develop a simulation model that allows integration of data from different sources to calculate the incremental cost-effectiveness and cost-utility of new treatments for overactive bladder. The model compares tolterodine, a new treatment that aims at alleviating symptoms and improving patients' quality of life, to no treatment. Simulations for Sweden are presented as an example. The Markov model combines clinical, observational, and economic data. Markov states are defined based on severity of symptoms of overactive bladder (frequency of voids and leaks). Specific costs for drug treatment and use of sanitary protections as well as utilities are assigned for each state. The effectiveness of tolterodine is based on controlled clinical trials and open long-term extensions of these trials. Outcome is measured as quality-adjusted life years (QALYs) and as the number of months spent in a state with no or very limited symptoms. During the course of 1 year, patients treated with tolterodine spend more time in states with no or limited symptoms compared to those receiving no treatment. Tolterodine-treated patients having a better quality of life during the year. The mean utility of the treated cohort is 0.70, compared to 0.67 in the no-treatment cohort, which is equivalent to the entire cohort moving by one level to a state with less severe symptoms. Mean total costs per patient in the tolterodine arm are SEK8,595 (US $1,131; 1 US$ = 7.6 SEK) compared to SEK3,286 (US$432) in the no-treatment arm. The extra cost due to tolterodine is SEK380 (US$50) per month, which falls within the range of monthly amounts that patients were willing to pay out of pocket for a 25 or 50% improvement of their symptoms in a previous study. The cost for pads is reduced by 23%. The marginal cost per QALY gained with tolterodine is estimated at SEK213,000 (US$28,000). Based on this simulation model, it appears that treatment of overactive bladder with a well-tolerated pharmacological treatment such as tolterodine is cost-effective.