Background: Analysis of EQ-5D data often focuses on changes in utility, ignoring valuable information from other parts of the instrument. The objective was to explore how the utility index, EQ-5D profile, and EQ-VAS captured change in clinical trials of mirabegron, a new treatment for overactive bladder (OAB).
Data: Data were pooled from three phase III clinical trials that investigated the efficacy and safety of mirabegron vs placebo. Tolterodine ER 4 mg was included as an active control in one study: (1) placebo, mirabegron 50 mg and 100 mg, and tolterodine 4 mg ER; (2) placebo, mirabegron 50 mg and 100 mg; (3) placebo, and mirabegron 25 mg and 50 mg. Data were collected at baseline, week 4, 8, and 12.
Methods: Analyses were performed on full analysis and modified intention to treat (ITT) data sets using UK utilities. Analysis controlled for relevant patient characteristics. Analysis of Covariance identified changes from baseline at each time point in utilities and EQ-VAS. Areas Under the Curve were estimated to summarize inter-temporal differences in effect. EQ-5D profile data were analysed using the Paretian Classification of Health Change.
Results: In modified ITT analyses, mirabegron 50 mg was superior to tolterodine 4 mg in changes from baseline utilities after 12 weeks (p < 0.05); similarly, AUC results showed mirabegron 50 mg to be superior to tolterodine (p < 0.05) and placebo (p < 0.05) with the benefit already apparent at 4 weeks (p < 0.05). EQ-VAS more consistently indicated superior outcomes: all three mirabegron doses showed statistically significant greater effectiveness compared to tolterodine at 12 weeks. Individual EQ-5D dimensions and the overall profile showed no significant differences between study arms.
Conclusion: Mirabegron showed quicker and superior improvement in HR-QoL compared to tolterodine 4 mg ER. A limitation of the study is that EQ-5D was a secondary outcome in the pivotal trials, which were not powered to measure differences on EQ-5D.