OBJECTIVES: Degarelix is the first gonadotrophin-releasing hormone (GnRH) antagonist to be launched in the UK for first-line treatment of advanced prostate cancer. The aim of this evaluation was to predict long-term clinical and economic outcomes from treatment with degarelix compared to treatment with goserelin, standard current practice, from the perspective of NHS Scotland. METHODS: Analyses were conducted using a 20 year semi-Markov (cohort health-state transition) cost-utility model which was recently submitted to and accepted by the Scottish Medical Consortium (SMC). The model considers two patient groups – the intention-to-treat population (ITT) of patients with hormone-responsive prostate cancer in whom treatment with androgen-deprivation therapy is indicated and who would be prescribed a LHRH agonist and a high-risk population with a baseline PSA level >20ng/ml. Probabilistic and deterministic sensitivity analyses were conducted to assess uncertainty in the model. RESULTS: The key benefit of treatment with degarelix comes from keeping patients in the first-line treatment state for longer, incurring less time and costs in the later more costly and lower utility non-hormonal therapy state. At NHS list-price degarelix is estimated to dominate treatment with goserelin within both populations with a saving of £271 and QALY gain of 0.46 in the ITT population. Probabilistic sensitivity analyses show that degarelix is likely to be cost-effective (at a willingness-to-pay of £500 per QALY) in 100% of cases. CONCLUSIONS: The economic analysis shows that degarelix not only provides a better patient outcome but is also less costly than goserelin over a lifetime of treatment. It is rare for a new treatment to predict dominance over existing therapies – only 18% of SMC submissions up to 2011 have predicted dominance. In addition degarelix shows a large gain in quality of life (almost half a year in full health) even when a conservative assumption of no increase in survival is applied.