Analytical approach:
A Markov model was used to simulate the natural history and to provide projections of possible outcomes and costs for the two treatment strategies. The time horizon of the study was the lifetime of the patient. The authors reported that the perspective adopted in the economic analysis was that of the UK National Health Service (NHS).
Effectiveness data:
The effectiveness data were derived from clinical studies conducted at InSightec (the manufacturing company of MRgFUS). The results from these studies were combined and the outcomes were extrapolated to a lifetime, using transitional probabilities of recurrence derived from the literature. The main clinical effectiveness estimate was the relationship between nonperfused volume (NPV), relative to the total fibroids volume, and the rate of the alternative treatment.
Monetary benefit and utility valuations:
The utility estimates were derived from one of the InSightec trials and were taken at six months after treatment for patients undergoing MRgFUS. The quality of life score was derived using the SF-36 and converted into a utility value using the SF-6D. Based on findings from published studies, the authors assumed that the quality of life score was the same for MRgFUS as for other treatments, and that this score did not change beyond six months after treatment.
Measure of benefit:
The measure of benefit was the number of quality-adjusted life-years (QALYs) gained.
Cost data:
The direct costs were those relating to initial and subsequent hospitalisations and outpatient services such as day procedures, diagnostic tests, medical personnel and medication costs and equipment. The hospital costs of MRgFUS were derived from estimates of resource use obtained from a hospital trust in London. In order to generalise the costs to the UK, these costs were adjusted to UK average prices using the Market Forces Factor (MFF). Other hospital costs and resource use data were mainly derived from published estimates. The unit costs were obtained from the NHS Reference Costs and the Personal Social Services Research Unit. The medication costs were obtained from the British National Formulary and the Scottish Prescription Cost Analysis. All costs were reported in UK pounds sterling (£). As they could be incurred over the lifetime of the patient, discounting was performed using an annual rate of 3.5%.
Analysis of uncertainty:
The uncertainty in the model was evaluated using a series of one-way and two-way sensitivity analyses by varying the definition of current practice, the NPV ratio, the age of patients, the number of procedural deaths, the recurrence rates, the complication rates, the quality of life, and the treatment costs. In addition, probabilistic sensitivity analyses, where probability distributions are presented for each parameter, were also performed. The results of these analyses were presented using cost-effectiveness acceptability curves.