Analytical approach:
The evaluation used a short-term decision tree, which modelled patients from the start of treatment to the end of month one, followed by a Markov model, which evaluated patients from the end of month one up to 10 years (the lifetime of the patient). The authors reported that the perspective was that of the NHS.
Effectiveness data:
The clinical and effectiveness data were from published studies and the opinion of local clinicians. The main difference in effectiveness between the two interventions was that triptorelin caused an initial flare that could lead to serious clinical symptoms requiring hormone treatment. The two major complications were spinal cord compression and bladder outlet obstruction. Complication rates were from published studies or the opinion of local clinicians.
Monetary benefit and utility valuations:
The utility estimates were from published sources. The adverse events, other than those from the initial flare, were assumed to have a similar impact on quality of life with each treatment.
Measure of benefit:
Quality-adjusted life-years (QALYs) were the summary measure. Future benefits were discounted at an annual rate of 3.5%.
Cost data:
The direct costs analysed were those of the drugs, their administration, and the treatment of significant events as a result of the initial flare. These costs were from the British National Formulary, published health and social care reference costs, NHS health-related group costs, and national reports. Future costs were discounted at an annual rate of 3.5%. All costs were reported in UK £.
Analysis of uncertainty:
One- and multi-way sensitivity analyses were undertaken by varying individual parameters. A probabilistic sensitivity analysis was conducted to assess the uncertainty of the results when varying all uncertain inputs simultaneously. For this analysis, probability distributions were fitted for every model parameter and 10,000 simulations were performed.