Abstract and Introduction
Abstract
Background and Objective: Imatinib mesylate is the first effective therapy for advanced unresectable gastrointestinal stromal tumours (GIST). Adoption of this therapy in clinical practice is partly dependent on reimbursement by third-party payers in many countries. The objective of this study was to estimate the cost effectiveness of imatinib mesylate in the treatment of GIST.
Methods: A cost-effectiveness model of GIST treatment was developed. Long- term survival and duration of imatinib mesylate benefit were projected by fitting curves to 52-month follow-up data from a phase II clinical trial of imatinib and projecting weekly probabilities of survival and continued treatment over 10 years. Weekly cost estimates in 2005 US dollars included cost of imatinib mesylate 400 mg/day ($US685), other medical services for imatinib mesylate-treated patients ($US359) and palliative care for patients in the end stage of GIST ($US2575). Utility associated with successful treatment was estimated at 0.935 and that of treatment failure and progressive disease at 0.875. Costs, life-years and quality- adjusted life-years (QALYs) were calculated over the 10-year time horizon and discounted to treatment initiation at an annual rate of 3%.
Results: Imatinib mesylate therapy for unresectable GIST was projected to increase life expectancy to 5.8 years, an increase of 2.7 years over the control group. This translated into an increase of 1.9 QALYs at a marginal cost of $US74,369, yielding a cost-effectiveness ratio of $US38,723 per QALY. Cost effectiveness was not very sensitive to model parameters other than the cost of imatinib mesylate itself.
Conclusion: The cost effectiveness of imatinib mesylate in the treatment of GIST is within the commonly accepted range for life-saving interventions, based on US data.
Introduction
Gastrointestinal stromal tumours (GIST) are soft-tissue tumours of the gastrointestinal tract, most commonly of gastric origin, that express the activated transmembrane kit receptor that leads to dysfunctional tyrosine kinase activity.[1,2,3,4] These tumours are initially treated by surgical resection but recurrence and metastasis are common, with prognosis influenced by mitotic rate, tumour size and anatomical site.[5] Until recently, the prognosis for patients with advanced unresectable or metastatic GIST has been poor.[6,7]
Imatinib mesylate is a tyrosine kinase inhibitor that blocks the kit receptors and platelet-derived growth factor receptor-a kinase activity and consequently suppresses the signal transduction pathways linked to cell proliferation and resistance to apoptosis.[8] Imatinib mesylate has been shown in clinical trials to be a safe and effective treatment in patients with advanced GIST.[9,10] Among patients who participated in the phase II multicentre trial that provided the clinical basis for regulatory approval of the drug, estimated 1-year survival was 88%.[9] In contrast, among a similar series of 100 GIST patients with incomplete tumour resection who did not receive imatinib mesylate, including 74 with metastatic disease, only 50% survived to 12 months.[11]
As with any novel medical technology, the circumstances in which patients can be reimbursed by healthcare payers can depend on economic assessments that weigh the costs and benefits of the treatment. Recent advances in cancer therapeutics in particular are attracting scrutiny because of the relative costs of new drugs compared with traditional cytotoxic agents.[12] An economic evaluation of imatinib mesylate for treatment of unresectable and/or metastatic GIST was recently published by the Health Technology Assessment Programme of the UK National Health Service.[13] The cost effectiveness of imatinib mesylate was reported to be in the range of £21,404-£33,976 per quality-adjusted life-year (QALY) gained. This is within the range (£20,000-£35,000) of societal willingness to pay for a medical treatment inferred by previous National Institute for Health and Clinical Excellence (NICE) decisions. However, economic evaluations may not be generalisable beyond national healthcare markets, given geographic variation in treatment practices and medical resource costs, and hence the cost effectiveness of imatinib mesylate outside the UK remains uncertain. Furthermore, a median of 52 months of follow-up data in the imatinib mesylate trial is now available,[14] compared with the 25 months on which the UK analysis was based, affording more robust survival projections. We therefore report an analysis of the cost-effectiveness of imatinib mesylate for the management of patients with unresectable or metastatic GIST, from a US societal perspective, with effectiveness expressed in terms of health-related utility (quality-adjusted survival). Our analysis is partly based upon the survival experience of a cohort of patients followed in a pivotal clinical trial.[9,14]
Clin Drug Invest. 2007;27(2):85-93. © 2007 Adis Data Information BV
Cite this: Cost Effectiveness of Imatinib Mesylate in the Treatment of Advanced Gastrointestinal Stromal Tumours - Medscape - Feb 01, 2007.
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