Economic evaluation of minimal access surgery : the case of surgical treatment for menorrhagia
The purpose of this thesis is to explore the methodological and empirical issues relating to the economic evaluation of minimal access surgery (MAS). Given the likely increase in the utilisation of economic analysis in this area, it is crucial to explore whether the methods of economic evaluation have limitations in the face of the particular characteristics of MAS. The comparison of abdominal hysterectomy (AH) and transcervical endometrial resection (TCRE), for the treatment of menorrhagia, is used as a vehicle to develop methods in relation to MAS. Having reviewed the literature and issues relating to the economic analysis of this group of technologies, the empirical starting point of the thesis is the assessment of the limitations of economic evaluations alongside clinical trials, using a trial comparing AH and TCRE. Three major areas of weakness are identified, and alternative ways of addressing these weaknesses are explored in the remainder of the thesis. The first area of methodological development relates to the measure of benefit used in economic evaluation of MAS. In this clinical context, it is argued that the trade-offs that exist between MAS and conventional surgery, in terms of process characteristics and outcomes, should result in an important role for patients' preferences in the construction of a benefit measure. A cost-utility analysis using the standard quality-adjusted life year (GALY) is undertaken, using trial data augmented with valuation data from a further study. The lack of consistency between individual preferences and standard QALYs suggests a major weakness with this measure of benefit. The strengths and weaknesses of an alternative measure of benefit in cost-utility analysis - the ex ante healthy years equivalent (HYE) - are assessed based on a further valuation study. It is shown that it is feasible to elicit ex ante HYEs from patients and that this measure of benefit exhibits some consistency with other expressions of patients' preferences. However, the HYE is likely to impose a greater measurement burden than the standard QALY. The second area of methodological development in the thesis is the analysis of the generalisability of trial-based economic evaluation, given the limitations that often exist with the external validity of trials. A framework is developed within which trial and observational data can be synthesised. This facilitates the use of sensitivity analysis to explore the robustness of base-case (trial-generated) results to alternative sources of data, which may be more representative of routine practice. The third area of methodological development stems from the importance of patients' preferences in relation to MAS. This element relates to the use of methods to model and to evaluate management strategies which use patients' preferences to determine treatment allocation. It is concluded that preference-based decision making has the potential to be cost effective in relation to TCRE and AH, and MAS applications more generally. The thesis demonstrates the importance of continued development in the detailed methods of economic evaluation.