706P - Cost-Effectiveness Analysis of Three Year versus One Year Imatinib for the Treatment of Patients at High Risk of Disease Recurrence Following Surgical Resection of Kit (CD117) Positive Gastrointestinal Stromal Tumours (GIST)

Abstract

ABSTRACT Background Imatinib is licensed for the adjuvant treatment of adult patients who are at significant risk of disease recurrence following resection of KIT (CD117) positive GIST. The SSG Phase III trial has shown significant survival benefits for patients who received three years of treatment with Glivec® (imatinib) after surgery to remove KIT (CD117)-positive GIST (KIT+ GIST) compared to one year of treatment. Aim: To evaluate the cost-effectiveness of three years' imatinib adjuvant therapy in comparison with one year therapy for adult patients at high risk of disease recurrence following surgical resection of KIT (CD117) positive GIST in Scotland. Methods The economic model predicts long-term survival for patients on three years of adjuvant imatinib compared with those on one year of therapy. A Markov state-transition model was used to simulate patient pathways over a lifetime horizon. Patients were grouped into three primary health states: (1) free of recurrent GIST; (2) recurrent GIST; and (3) death (from GIST or other causes). Efficacy data were derived from a retrospective review of the SSG study to identify high risk patients, as defined by the Miettinen risk criteria. Costs (drug costs, hospital appointments for administration and monitoring, and treatment for adverse events) and health related quality of life values were assigned to each health state. Cost-effectiveness was expressed in terms of incremental cost per quality-adjusted life-years (QALYs) gained. Results Three years of adjuvant imatinib therapy for patients at high risk of recurrence was predicted to achieve an additional 1.58 QALYS compared with one year of treatment. These health benefits are gained at an estimated incremental cost per QALY of £14,108. These results were robust to changes in key model parameters. Conclusions The analysis suggests that, for patients at high risk of recurrence following surgical resection of localised GIST, three years of adjuvant imatinib treatment leads to improved long term quality-adjusted survival compared with one year's therapy. Extended adjuvant treatment with imatinib represents good value for money according to currently accepted standards of cost-effectiveness in Scotland. Disclosure L. Gray: I am an employee of Novartis Pharmaceuticals UK Ltd, manufacturer of imatinib. All other authors have declared no conflicts of interest.