PCN86 - Comparing Cost-Effectiveness Results from A Manufacture Submitted Versus Restructured Single Technology Appraisal Decision Analytical Model: An Example from the Nice

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Manufacturer submitted cost-effectiveness models for appraisal might be subject to structural uncertainty. However, methods dealing with structural uncertainties in a decision model are not well-developed. This study examines results from a restructured single technology appraisal cost-effectiveness model, submitted to the National Institute for Health and Care Excellence (NICE), of Erlotinib (versus Best Supportive Care) as a maintenance therapy for patients with non-small cell lung cancer. The Evidence Review Group (ERG) criticized the manufacturer’s ‘Markov’ model for not being governed by transition probabilities. It used an independent projective survival functions for progression-free survival and overall survival, which led a negative post-progression survival (PPS) estimate to appear in later cycles. This study employs three fixed- and time-varying approaches to estimate state transition probabilities of the restructured model using published summary survival data. The time-varying parametric approach estimates post-progression probabilities and probabilities of death for Erlotinib differently than fixed-transition approaches. The best fitting curves are achieved for both PPS and probability of death across the time for which data were available, but the curves start diverging towards the end of this period. The alternative (Markov) model which extrapolates the curves forward in time suggests that this difference between a time-varying and fixed-transition becomes even greater. The alternative models produce an Incremental Cost-Effectiveness Ratio (ICER) of £54000 -£66000 per quality adjusted life year (QALY) gain, which is comparable to an ICER presented in the manufacturer’s model (£55000/QALY gain). The cost-effectiveness results from restructured alternative models are in line with those produced in the manufacturer submission; however, in terms of the magnitude they vary. A wide range of variation in cost-effectiveness results produced by restructured models might be crucial for interventions falling close to a willingness-to-pay threshold value.